Random access in next generation wireless systems

ABSTRACT

A wireless transmit/receive unit (WTRU) may initiate a random access. The WTRU may determine whether to select a first random access channel (RACH) procedure or a second RACH procedure for the random access. The first RACH procedure may be a legacy RACH procedure. The second RACH procedure may be an enhanced RACH (eRACH) procedure. The WTRU may determine whether to select the first RACH procedure or the second RACH procedure based at least on a type of uplink data to be transmitted. When the second RACH procedure is selected, the WTRU may determine at least one physical random access channel (PRACH) resource associated with the second RACH procedure. The WTRU may determine a preamble sequence associated with the second RACH procedure. The WTRU may determine a data resource for the uplink data. The WTRU may send a RACH transmission that includes the preamble sequence and the uplink data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/314,666, filed Jan. 1, 2019, which is based on PCT filingPCT/US2017/054073, filed Sep. 28, 2017, which claims priority to U.S.provisional patent application No. 62/401,082, filed Sep. 28, 2016, U.S.provisional patent application No. 62/416,237, filed Nov. 2, 2016, andU.S. provisional patent application No. 62/474,762, filed Mar. 22, 2017,which are incorporated herein by reference in their entirety.

BACKGROUND

Mobile communications continue to evolve. A fifth generation may bereferred to as 5G. A previous (legacy) generation of mobilecommunication may be, for example, fourth generation (4G) long termevolution (LTE).

SUMMARY

Systems, methods, and instrumentalities (e.g. in a wirelesstransmit/receive unit (WTRU) and/or network layers L1, L2, L3) aredisclosed for random access in next generation wireless systems. A WTRUmay initiate a random access request. The WTRU may initiate the randomaccess request to perform a scheduling request and/or transmit an amountof data that is below a predetermined threshold. The WTRU may determinewhether to select a first random access channel (RACH) procedure or asecond RACH procedure for the random access. The first RACH proceduremay be a legacy RACH procedure. The second RACH procedure may be anenhanced RACH (eRACH) procedure. The WTRU may determine whether toselect the first RACH procedure or the second RACH procedure based on atype of uplink data to be transmitted and/or the purpose of the randomaccess request.

When the second RACH procedure is selected, the WTRU may determine atleast one physical random access channel (PRACH) resource associatedwith the second RACH procedure. The PRACH resource may be an enhancedPRACH resource. The PRACH resource may include one or more of thepreamble sequence, a time-frequency resource, and/or a numerology. TheWTRU may determine a preamble sequence associated with the second RACHprocedure. The preamble sequence may be determined based on one or moreof the at least one PRACH resource, a data reception reliability, anamount of data to be transmitted, a maximum transport block size, arange of allowable transport block sizes, a type of the RACHtransmission, a trigger associated with the RACH transmission, a timingrequirement, a buffer status, a WTRU identity, a location, a numerology,a modulation and coding scheme (MCS), a demodulation configuration,and/or multiple preambles received from the network device.

The WTRU may determine a data resource for the uplink data based on oneor more of the at least one PRACH resource, the preamble sequence, thetype of uplink data, or a size of the uplink data. The data resource maybe determined from a set of available resources. The set of availableresources may be indicated via one or more of system information, anaccess table, or a physical data control channel (PDCCH) grant to aspecific radio network identifier (RNTI). The WTRU may send a RACHtransmission to a network device using the at least one PRACH resourceand/or the data resource. The RACH transmission may include the preamblesequence and/or the uplink data. The preamble sequence and the uplinkdata may be disjoint in time and/or frequency. The preamble sequence maybe prepended to the uplink data. The WTRU may receive a random accessresponse (RAR) message that includes an acknowledgment (ACK) or anegative acknowledgment (NACK) associated with the uplink data in theRACH transmission. The RAR message may include an uplink grant. The WTRUmay transmit additional pending uplink data, control information, and/orstate transition information to the network device based on the uplinkgrant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 1A according to an embodiment;

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A according to an embodiment;

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A according to an embodiment

FIG. 2 is an example of transmission bandwidths.

FIG. 3 is an example of spectrum allocation where different subcarriersmay be assigned to different modes of operation.

FIG. 4 is an example of timing relationships for time division duplex(TDD) duplexing.

FIG. 5 is an example of timing relationships for frequency divisionduplex (FDD) duplexing.

FIG. 6 is an example of an enhanced random access channel (eRACH)procedure.

FIG. 7 is an example of a demodulation configuration.

FIG. 8 is an example flow chart of determining whether to perform aneRACH procedure or a legacy RACH procedure.

DETAILED DESCRIPTION

A detailed description of illustrative embodiments will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be exemplary and in no way limitthe scope of the application.

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a RAN104/113, a CN 106/115, a public switched telephone network (PSTN) 108,the Internet 110, and other networks 112, though it will be appreciatedthat the disclosed embodiments contemplate any number of WTRUs, basestations, networks, and/or network elements. Each of the WTRUs 102 a,102 b, 102 c, 102 d may be any type of device configured to operateand/or communicate in a wireless environment. By way of example, theWTRUs 102 a, 102 b, 102 c, 102 d, any of which may be referred to as a“station” and/or a “STA”, may be configured to transmit and/or receivewireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106/115, the Internet110, and/or the other networks 112. By way of example, the base stations114 a, 114 b may be a base transceiver station (BTS), a Node-B, an eNodeB, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller,an access point (AP), a wireless router, and the like. While the basestations 114 a, 114 b are each depicted as a single element, it will beappreciated that the base stations 114 a, 114 b may include any numberof interconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104/113, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals on one or morecarrier frequencies, which may be referred to as a cell (not shown).These frequencies may be in licensed spectrum, unlicensed spectrum, or acombination of licensed and unlicensed spectrum. A cell may providecoverage for a wireless service to a specific geographical area that maybe relatively fixed or that may change over time. The cell may furtherbe divided into cell sectors. For example, the cell associated with thebase station 114 a may be divided into three sectors. Thus, in oneembodiment, the base station 114 a may include three transceivers, i.e.,one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and mayutilize multiple transceivers for each sector of the cell. For example,beamforming may be used to transmit and/or receive signals in desiredspatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104/113 and the WTRUs 102 a,102 b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 115/116/117 using wideband CDMA (WCDMA).WCDMA may include communication protocols such as High-Speed PacketAccess (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-SpeedDownlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro):

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using New Radio (NR).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., a eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (I5-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106/115.

The RAN 104/113 may be in communication with the CN 106/115, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. The data may have varying qualityof service (QoS) requirements, such as differing throughputrequirements, latency requirements, error tolerance requirements,reliability requirements, data throughput requirements, mobilityrequirements, and the like. The CN 106/115 may provide call control,billing services, mobile location-based services, pre-paid calling,Internet connectivity, video distribution, etc., and/or performhigh-level security functions, such as user authentication. Although notshown in FIG. 1A, it with be appreciated that the RAN 104/113 and/or theCN 106/115 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 104/113 or a different RAT. Forexample, in addition to being connected to the RAN 104/113, which may beutilizing a NR radio technology, the CN 106/115 may also be incommunication with another RAN (not shown) employing a GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106/115 may also serve as a gateway for the WTRUs 102 a, 102 b,102 c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104/113 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors, the sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor; an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, and/ora humidity sensor.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) anddownlink (e.g., for reception) may be concurrent and/or simultaneous.The full duplex radio may include an interference management unit toreduce and or substantially eliminate self-interference via eitherhardware (e.g., a choke) or signal processing via a processor (e.g., aseparate processor (not shown) or via processor 118). In an embodiment,the WRTU 102 may include a half-duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for either the UL (e.g., for transmission) or thedownlink (e.g., for reception)).

FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the aft interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (or PGW) 166. While each of the foregoing elements are depictedas part of the CN 106, it will be appreciated that any of these elementsmay be owned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have an access or an interface to a DistributionSystem (DS) or another type of wired/wireless network that carriestraffic in to and/or out of the BSS. Traffic to STAs that originatesfrom outside the BSS may arrive through the AP and may be delivered tothe STAs. Traffic originating from STAs to destinations outside the BSSmay be sent to the AP to be delivered to respective destinations.Traffic between STAs within the BSS may be sent through the AP, forexample, where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be considered and/or referred to as peer-to-peertraffic. The peer-to-peer traffic may be sent between (e.g., directlybetween) the source and destination STAs with a direct link setup (DLS).In certain representative embodiments, the DLS may use an 802.11e DLS oran 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS)mode may not have an AP, and the STAs (e.g., all of the STAs) within orusing the BSS may communicate directly with each other. The IBSS mode ofcommunication may sometimes be referred to herein as an “ad-hoc” mode ofcommunication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling.The primary channel may be the operating channel of the BSS and may beused by the STAs to establish a connection with the AP. In certainrepresentative embodiments, Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA) may be implemented, for example in in 802.11systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, maysense the primary channel. If the primary channel is sensed/detectedand/or determined to be busy by a particular STA, the particular STA mayback off. One STA (e.g., only one station) may transmit at any giventime in a given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications, such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel, If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode), transmitting to the AP, the entire available frequency bands maybe considered busy even though a majority of the frequency bands remainsidle and may be available.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the RAN 113 and the CN 115according to an embodiment. As noted above, the RAN 113 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 113 may also be in communication with theCN 115.

The RAN 113 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 113 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement MIMO technology. For example,gNBs 180 a, 108 b may utilize beamforming to transmit signals to and/orreceive signals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a,for example, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs 180 a, 180 b, 180 c may implement carrier aggregationtechnology. For example, the gNB 180 a may transmit multiple componentcarriers to the WTRU 102 a (not shown). A subset of these componentcarriers may be on unlicensed spectrum while the remaining componentcarriers may be on licensed spectrum. In an embodiment, the gNBs 180 a,180 b, 180 c may implement Coordinated Multi-Point (CoMP) technology.For example, WTRU 102 a may receive coordinated transmissions from gNB180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containingvarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, dual connectivity, interworkingbetween NR and E-UTRA, routing of user plane data towards User PlaneFunction (UPF) 184 a, 184 b, routing of control plane informationtowards Access and Mobility Management Function (AMF) 182 a, 182 b andthe like. As shown in FIG. 1D, the gNBs 180 a, 180 b, 180 c maycommunicate with one another over an Xn interface.

The CN 115 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a, 184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whileeach of the foregoing elements are depicted as part of the CN 115, itwill be appreciated that any of these elements may be owned and/oroperated by an entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different PDU sessions with differentrequirements), selecting a particular SMF 183 a, 183 b, management ofthe registration area, termination of NAS signaling, mobilitymanagement, and the like. Network slicing may be used by the AMF 182 a,182 b in order to customize CN support for WTRUs 102 a, 102 b, 102 cbased on the types of services being utilized WTRUs 102 a, 102 b, 102 c.For example, different network slices may be established for differentuse cases such as services relying on ultra-reliable low latency (URLLC)access, services relying on enhanced massive mobile broadband (eMBB)access, services for machine type communication (MTC) access, and/or thelike. The AMF 162 may provide a control plane function for switchingbetween the RAN 113 and other RANs (not shown) that employ other radiotechnologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP accesstechnologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN115 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 115 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating UE IP address,managing PDU sessions, controlling policy enforcement and QoS, providingdownlink data notifications, and the like. A PDU session type may beIP-based, non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering downlink packets, providing mobility anchoring, and thelike.

The CN 115 may facilitate communications with other networks. Forexample, the CN 115 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 115 and the PSTN 108. In addition, the CN 115may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a localData Network (DN) 185 a, 185 b through the UPF 184 a, 184 b via the N3interface to the UPF 184 a, 184 b and an N6 interface between the UPF184 a, 184 b and the DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or may performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RE circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

A 5G (e.g., 5G Flex) air interface may support a variety of use cases,such as one or more of the following: (i) improved broadband (IBB)performance; (ii) industrial control and communications (ICC) andvehicular applications (V2X) and (iii) massive machine-typecommunications (mMTC). The terms 5G interface or 5G Flex may be usedherein to refer to an air interface used to provide next generationradio access. The terms 5G interface or 5G Flex may be a relativelydynamic interface based on the varying use of different numerologies tosupport different types of transmissions. An example of transmissionsparameters that may be varied for different numerologies may include oneor more of a subcarrier spacing, a symbol (e.g., OFDM symbol) length, atransmission time interval (TTI) length, a waveform type, and/or thelike. The term New Radio (NR) may also be used to refer to a 5Ginterface or 5G Flex.

A 5G interface may provide support for ultra-low transmission latency(LLC). Air interface latency may be, for example, 1 ms round trip time(RTT). TTIs may be, for example, between 100 us and 250 us. Support maybe provided for ultra-low access latency (e.g., time from initial systemaccess until completion of transmission of a first user plane dataunit). End-to-end (e2e) latency (e.g., of less than 10 ms) may besupported for IC and V2X.

A 5G interface may provide support for ultra-reliable transmission(URC). Support for URC may comprise, for example, a transmission successand service availability (e.g., 99.999% or a Packet Loss Ratio less than10e-6) and/or a speed mobility range (e.g., 0-500 km/h). A packet lossratio (e.g. less than 10e⁻⁶) may be supported for IC and V2X.

A 5G interface may provide support for MTC operation. Support forMachine-Type Communications (MTC) operation may comprise, for example,air interface support for narrowband operation (e.g., less than 200KHz), extended battery life (e.g. 15 years of autonomy) and/or minimalcommunication overhead for small and infrequent data transmissions(e.g., low data rate such as 1-100 kbps with access latency of secondsto hours).

Orthogonal Frequency-Division Multiplexing (OFDM) may be used as asignal format for data transmissions, for example, in LTE and IEEE802.11. OFDM may (e.g., efficiently) divide spectrum into multipleparallel orthogonal subbands. A (e.g., each) subcarrier may be shapedusing a rectangular window in the time domain, which may lead tosine-shaped subcarriers in the frequency domain. Orthogonal FrequencyDivision Multiple Access (OFDMA) may be implemented with (e.g. perfect)frequency synchronization and (e.g. tight) management of uplink timingalignment within the duration of a cyclic prefix, for example, tomaintain orthogonality between signals and to minimize intercarrierinterference. Tight synchronization may be a challenge, for example, ina system where a WTRU may be simultaneously connected to multiple accesspoints. Additional power reduction may be applied to uplinktransmissions, e.g., to comply with spectral emission requirements inadjacent bands, which may occur in the presence of aggregation offragmented spectrum for a WTRU's transmissions.

Some shortcomings of OFDM (e.g. cyclic prefix (CP)-OFDM) implementationsmay be addressed, for example, by applying more stringent RFrequirements, such as when operating with a large contiguous spectrumwithout requiring aggregation. A CP-based OFDM transmission scheme maylead to a downlink physical layer for 5G similar to precedinggenerations, such as modifications to pilot signal density and location.

A 5gFLEX implementation may utilize OFDM or waveforms other than OFDMfor 5G systems, e.g., for a downlink transmission scheme.

One or more principles that may be applicable to the design of flexibleradio access for 5G are described herein, e.g., based on OFDMA and LTEsystems. Examples provided herein may be applicable to other wirelesssystems and/or wireless technologies.

A 5gFLEX downlink transmission scheme may be based on a multicarrierwaveform that may be characterized by high spectral containment (e.g.lower side lobes and lower Out-Of-Band (OOB) emissions). MC waveformcandidates for 5G may include OFDM—Offset Quadrature AmplitudeModulation (OQAM) and universal filtered multi-carrier (UFMC) (e.g.UF-OFDM) among other waveforms. Examples provided herein may useOFDM-OQAM and UFMC (UF-OFDM), but subject matter (e.g. examples) may beapplicable to other waveforms.

Multicarrier modulation waveforms may divide a channel into subchannelsand may modulate data symbols on subcarriers in the subchannels.

A filter may be applied (e.g. in the time domain per subcarrier) to anOFDM signal, e.g., for OFDM-OQAM to reduce OOB. OFDM-OQAM may cause verylow interference to adjacent bands. OFDM-OQAM may not need large guardbands. OFDM-OQAM may not require a cyclic prefix. OFDM-OQAM may be aFiltered Band Multi-Carrier (FBMC) technique. OFDM-OQAM may be sensitiveto multipath effects and to high delay spread in terms of orthogonality,which may complicate equalization and channel estimation.

A filter may be applied (e.g. in the time domain per subband) to an OFDMsignal, e.g., for UFMC (UF-OFDM) to reduce OOB. Filtering may be appliedper subband, for example, to use spectrum fragments, e.g., to reducecomplexity and improve practical implementation of UF-OFDM. There may beunused spectrum fragment in the band. OOB emissions in fragments may behigh. UF-OFDM may provide an improvement over OFDM at the edges of thefiltered spectrum with or without improvement in the spectral hole.

A waveform may enable multiplexing in frequency of signals withnon-orthogonal characteristics (such as different subcarrier spacing)and co-existence of asynchronous signals, e.g., without requiringcomplex interference cancellation receivers. A waveform may facilitateaggregation of fragmented pieces of spectrum in baseband processing, forexample, as a lower cost alternative to its implementation as part of RFprocessing.

Co-existence of different waveforms within the same band may besupported, for example, to support mMTC narrowband operation (e.g. usingSingle Carrier Multiple Access (SCMA)). Support may be provided for thecombination of different waveforms (e.g. CP-OFDM, OFDM-OQAM and UF-OFDM)within the same band, e.g., for all aspects and/or for downlink ariduplink transmissions. Co-existence may include transmissions usingdifferent types of waveforms between different WTRUs or transmissionsfrom the same WTRU (e.g. simultaneously, with some overlap orconsecutive transmission in the time domain).

Other co-existence aspects may include support for hybrid types ofwaveforms, such as waveforms and/or transmissions that support apotentially varying CP duration (e.g. from one transmission to another)a combination of a CP and a low power tail (e.g. a zero tail), a form ofhybrid guard interval (e.g. using a low power CP) and/or an adaptive lowpower tail, etc. Hybrid types of waveforms may support dynamic variationand/or control of further aspects, such as how to apply filtering.Filtering may be applied at the edge of the spectrum used for receptionof any transmission(s) for a given carrier frequency, at the edge of aspectrum used for reception of a transmission associated to a specificSOM, or per subband or per group thereof.

An uplink transmission scheme may use the same or a different waveformused for downlink transmissions.

Multiplexing transmissions to and from different WTRUs in the same cellmay be based on frequency division multiple access (FDMA) and timedivision multiple access (TDMA).

5G Flexible Radio Access Technology (5gFLEX) radio access may becharacterized, for example, as a very high degree of spectrumflexibility that enables deployment in different frequency bands withdifferent characteristics, such as different duplex arrangements,different and/or variable sizes of available spectrum (e.g. whethercontiguous and/or non-contiguous spectrum allocations in the same ordifferent bands). 5gFLEX radio access may support variable timingaspects, such as support for multiple TTI lengths and/or support forasynchronous transmissions,

TDD and FDD duplexing schemes may be supported, e.g., in a duplexingarrangement. Supplemental downlink operation (e.g. for FDD operation)may be supported, for example, using spectrum aggregation. FDD operationmay support full-duplex FDD and half-duplex FDD operation. Downlink(DL)/Uplink (UL) allocation (e.g. for TDD operation) may be dynamic(e.g. it may or may not be based on a fixed DL/UL frame configuration).The length of a DL or UL transmission interval may be set pertransmission opportunity.

A characteristic of a 5G air interface may be to enable the use ofdifferent transmission bandwidths on uplink and downlink, which may, forexample, range from a nominal system bandwidth to a maximum valuecorresponding to a system bandwidth.

Supported system bandwidths (e.g. for single carrier operation) may, forexample, include 5, 10, 20, 40 and 80 MHz. Supported system bandwidthsmay be any bandwidth in a given range (e.g. from a few MHz to 160 MHz.Nominal bandwidths may have one or more fixed values. Narrowbandtransmissions (e.g. up to 200 KHz) may be supported within the operatingbandwidth for MTC devices.

FIG. 2 is an example of transmission bandwidths. System bandwidth mayrefer to the largest portion of spectrum that may be managed by anetwork for a given carrier. A portion that a WTRU minimally supportsfor cell acquisition, measurements and initial access to the network maycorrespond to nominal system bandwidth. A WTRU may be configured with achannel bandwidth, which may be within the range of the entire systembandwidth. A WTRU's configured channel bandwidth may or may not includethe nominal part of the system bandwidth, e.g., as shown in FIG. 2.

Bandwidth flexibility may be achieved, for example, when all applicableRF requirements for a given maximum operating bandwidth in a band can bemet without the introduction of additional allowed channel bandwidthsfor that operating band, e.g., due to the efficient support of basebandfiltering of the frequency domain waveform.

Procedures may be provided to configure, reconfigure and/or dynamicallychange a WTRU's channel bandwidth for single carrier operation.Procedures may be provided to allocate spectrum for narrowbandtransmissions within a nominal system, system or configured channelbandwidth.

A physical layer of a 5G air interface may be band-agnostic and/or maysupport operation in licensed bands below 5 GHz and/or operation inunlicensed bands in the range 5-6 GHz. Listen-Before-Talk (LBT) Cat 4based channel access framework, e.g., similar to LTE License AssistedAccess (LAA), may be supported, for example, for operation in unlicensedbands.

Cell-specific and/or WTRU-specific channel bandwidths for arbitraryspectrum block sizes may be scaled and managed, for example, usingscheduling, addressing of resources, broadcasted signals, measurements,etc.

Downlink control channels and signals may support FDM operation. A WTRUmay acquire a downlink carrier, for example, by receiving transmissionsusing (e.g. only) the nominal part of the system bandwidth. For example,a WTRU may not initially be required to receive transmissions coveringthe entire bandwidth that may be managed by the network for theconcerned carrier.

Downlink data channels may be allocated over a bandwidth that may or maynot correspond to a nominal system bandwidth, for example, withoutrestrictions other than being within the WTRU's configured channelbandwidth. For example, a network may operate a carrier with a 12 MHzsystem bandwidth using a 5 MHz nominal bandwidth, allowing devicessupporting (e.g. at most) 5 MHz maximum RF bandwidth to acquire andaccess the system while (e.g. potentially) allocating +10 to −10 MHz ofa carrier frequency to other WTRU's supporting (e.g.. up to) 20 MHzworth of channel bandwidth.

FIG. 3 is an example of spectrum allocation 300 where differentsubcarriers may be (e.g. at least conceptually) assigned to differentmodes of operation (e.g. spectrum operation mode (SOM)). Different SOMsmay be used, for example, to fulfill different requirements fordifferent transmissions. A SOM may, for example, consist of a subcarrierspacing, a TTI length and/or one or more reliability aspects (e.g. HARQprocessing aspects), a secondary control channel, etc. A SOM may be usedto refer to a (e.g. specific) waveform or may be related to a processingaspect (e.g. in support of co-existence of different waveforms in thesame carrier using Frequency Division Multiplexing (FDM) and/or TimeDivision Multiplexing (TDM)). A SOM may be used, for example, whencoexistence of Frequency Division Duplexing (FDD) operation in a TimeDivision Duplexing (TDD) band may be supported (e.g. in a TDM manner orsimilar manner).

A WTRU may be configured to perform transmissions according to one ormore SOMs. For example, a SOM may correspond to transmissions that useone or more of (i) a (e.g. specific) TTI duration, (ii) an initial powerlevel, (iii) a HARQ processing type, (iv) an upper bound for successfulHARQ reception/transmission, (v) a transmission mode, (vi) a physicalchannel (uplink or downlink), (vii) an operating frequency, band orcarrier, (viii) a specific waveform type or transmission according to aRAT (e.g. for 5G or previous generation LTE). A SOM may correspond to aQoS level and/or related aspect (e.g. maximum/target latency,maximum/target Block Error Rate (BLER) or similar). A SOM may correspondto a spectrum area and/or to a control channel or aspect thereof (e.g.search space, Downlink Control Information (DCI) type). For example, aWTRU may be configured with a SOM for (e.g. each of) an Ultra-ReliableCommunications (URC) type of service, a Low Latency Communication (LLC)type of service and/or a Massive Broadband Communications (MBB) type ofservice. A WTRU may have a configuration for a SOM for system accessand/or for transmission/reception of layer 3 (L3) control signaling(e.g. RRC), such as in a portion of a spectrum associated with thesystem (e.g. nominal system bandwidth).

Spectrum aggregation may be supported, for example, where a WTRUsupports transmission and reception of multiple transport blocks overcontiguous or non-contiguous sets of physical resource blocks (PRBs)within the same operating band (e.g. for single carrier operation).Mapping a single transport block to separate sets of PRBs may besupported. Support may be provided for simultaneous transmissionsassociated with different SOM requirements.

Support may be provided for multicarrier operation, e.g., usingcontiguous or non-contiguous spectrum blocks within the same operatingband or across two or more operating bands. Support may be provided foraggregation of spectrum blocks using different modes (e.g. FDD and TDD)and using different channel access methods (e.g. licensed and unlicensedband operation below 6 GHz). Support may be provided for procedures thatconfigure, reconfigure and/or dynamically change a WTRU's multicarrieraggregation.

Downlink and uplink transmissions may be organized into radio framescharacterized by a number of fixed aspects (e.g. location of downlinkcontrol information) and a number of varying aspects (e.g. transmissiontiming, supported types of transmissions).

A basic time interval (BTI) may be expressed in terms of an integernumber of one or more symbol(s), which symbol duration may be a functionof the subcarrier spacing applicable to the time-frequency resource.Subcarrier spacing (e.g. for an FDD frame) may differ between the uplinkcarrier frequency f_(UL) and the downlink carrier frequency f_(DL).

A transmission time interval (TTI) may be a minimum time supported by asystem between consecutive transmissions, for example, where each may beassociated with a different transport block (TB) for the downlink(TTI_(DL)) and the uplink (UL transceiver (TRx)), e.g., excluding anyapplicable preamble and including any control information (e.g. downlinkcontrol information (DCI) for downlink or uplink control information(UCI) for uplink). A TTI may be expressed in terms of an integer numberof one of more BTIs. A BTI may be specific to and/or associated with agiven SOM.

Frame duration support may, for example, include 100 us, 125 us (⅛ ms),142.85 us ( 1/7 ms may be 2 nCP LTE OFDM symbols) and 1 ms, e.g., toenable alignment of timing structures for one or more generations, suchas 5G and one or more previous generations of LTE.

A frame may start with downlink control information (DCI) of a fixedtime duration t_(dci) preceding a downlink data transmission (DL TRx)for a concerned carrier frequency—f_(UL+DL) for TDD and f_(DL) for FDD.

A frame may consist of a downlink portion (e.g. DCI and DL TRx) and(e.g. optionally) an uplink portion (e.g. UL TRx), for example, for FDDduplexing. A switching gap (swg) may (e.g. always) precede the uplinkportion of the frame, e.g., when present.

A frame may consist of a downlink reference TTI and one or more TTI(s)for the uplink, e.g., for FDD duplexing. The start of an uplink TTI maybe (e.g. always) derived using an offset (t_(offset)), which may beapplied from the start of the downlink reference frame that overlapswith the start of the uplink frame.

5gFLEX (e.g. for TDD) may support D2D/V2x/Sidelink operation in a frame,for example, by including respective downlink control and forwarddirection transmission in the DCI+DL TRx portion (e.g. when asemi-static allocation of the respective resources may be used) or inthe DL TRx portion (e.g. for dynamic allocation) and/or by including therespective reverse direction transmission in the UL TRx portion.

5gFLEX (e.g. for FDD) may support D2D/V2x/Sidelink operation in a UL TRxportion of a frame, for example, by including respective downlinkcontrol, forward direction and reverse direction transmissions in the ULTRx portion (e.g. dynamic allocation of the respective resources may beused).

Examples of frame structures may be shown in FIG. 4 (TDD) and FIG. 5(FDD). FIG. 4 is an example of timing relationships for TDD duplexing.FIG. 5 is an example of timing relationships for FDD duplexing.

A scheduling function may be supported in the MAC layer. There may be,for example, two scheduling modes: (1) network-based scheduling, e.g.,for tight scheduling in terms of resources, timing and transmissionparameters of downlink transmissions and/or uplink transmissions, and(2) WTRU-based scheduling, e.g., for more flexibility in terms of timingand transmission parameters. Scheduling information may be valid for asingle or for multiple TTIs, e.g., for one or both modes.

Network-based scheduling may enable a network to tightly manageavailable radio resources assigned to different WTRUs, e.g., to optimizethe sharing of resources. Dynamic scheduling may be supported.

WTRU-based scheduling may enable a WTRU to opportunistically accessuplink resources with minimal latency, e.g., on a per-need basis withina set of shared or dedicated uplink resources, which may be assigned(e.g. dynamically or statically) by the network. Support may be providedfor synchronized and/or unsynchronized opportunistic transmissions,Support may be provided for contention-based transmissions and/orcontention-free transmissions.

Support may be provided for opportunistic transmissions (e.g. scheduledor unscheduled), for example, to meet an ultra-low latency requirement(e.g. for 5G) and/or a power saving requirement (e.g. for an mMTC usecase).

Random access (e.g. in LTE) may be used, for example, for one or more ofthe following: (i) initial access (e.g. when establishing a radio link,such as moving from RRC_IDLE to RRC_Connected); (ii) to re-establish aradio link after radio link failure; (iii) for handover (e.g. whenuplink synchronization needs to be established to the new cell); (iv) toestablish uplink synchronization (e.g. when uplink or downlink dataarrives when the terminal is in RRC_Connected and the uplink may not besynchronized); (v) for positioning (e.g. using positioning procedure(s)based on uplink measurements) and/or (vi) as a scheduling request (e.g.when dedicated scheduling request resources have not been configured onPUCCH).

A random access attempt may be contention-based or contention-free. Forexample, a WTRU may perform a contention-based random access or acontention-free random access. A contention-based random access may usemultiple (e.g., four) steps. For example, a contention-based randomaccess may include the WTRU sending a random access preamble. The randomaccess preamble may allow an eNB to estimate transmission timing of aterminal. A contention-based random access may include a network sendinga timing advance command, for example, to adjust the terminaltransmission timing. The terminal transmission timing may be adjustedbased on the transmission timing estimated by the eNB. Acontention-based random access may include a transmission of a WTRUidentity to a network, e.g., along with control signaling by the WTRU. Acontention-based random access may include the network sending acontention resolution message to the WTRU.

There may be no need for contention resolution, for example, in acontention-free random access. A contention-free random access mayinclude a WTRU sending a random access preamble to a network and/or thenetwork sending a timing advance command in response to the randomaccess preamble. The timing advance command may indicate an adjustedterminal transmission timing.

A 5G air interface may support a wide variety of use cases (where eachmay have different QoS requirements), for example, in terms ofdifferentiation between applicable radio resources and transmissionprocedures (e.g. in terms of TTI duration, reliability, diversityapplied to the transmission and maximum latency).

Further QoS differentiation may be introduced between different datapackets, data flows and/or data bearers (or their equivalent), forexample, in terms of maximum guaranteed delay budget, packet error rateand data rate.

A MAC layer may handle functionality that may address the foregoing, forexample, to address one or more of the following: (i) satisfyingprerequisites for uplink transmissions; (ii) reduction of latencyassociated with uplink transmissions and/or (iii) Reduction of SignalingAssociated with Uplink Transmission.

Satisfaction of prerequisites for uplink transmissions may comprise, forexample, UL TA, positioning, WTRU speed and/or PL estimate. For example,a WTRU may manage and/or determine whether it has sufficientprerequisites to perform a given type of transmission, e.g., given usecases and transmission procedures.

Reduction of latency associated with uplink transmissions may beprovided. Uplink timing may be ensured through TA commands sent toCONNECTED WTRUs. This may not be practical for ULL devices that (e.g.only) communicate occasionally, for example, given that latency ofestablishing uplink timing may be too large. Moving to a new cell mayinvolve establishing uplink timing to the new cell, e.g., through RACH.Latency associated with uplink timing establishment for a ULLRC devicemay be avoided to support ULLRC.

Reduction of signaling associated with uplink transmission may beprovided. Uplink transmissions may involve maintaining or gaining uplinksynchronization, e.g., through a legacy RACH procedure. An mMTC use case(e.g. in 5G) may consist of having many WTRUs communicating to/with anetwork through short and occasional data transmissions. WTRUs may havevery long batter life (e.g. beyond 10 years) and may be able to operatein an area with a high connection density (e.g. 1,000,000 devices persquare kilometer): Signaling efficiency for 5G devices may (e.g. as aresult) be improved (e.g. in comparison with LTE).

A WTRU may be configured with an enhanced random access procedure. Anenhanced random access procedure may include less signaling between theWTRU and the network. An enhanced random access procedure may includetransmission of a first message (e.g., eMSG1) to the network andreception of a second message (e.g., eMSG2) from the network. The firstmessage may be an eRACH transmission.

An enhanced random access procedure may be beneficial for WTRUs that maynot be uplink synchronized, for example, to reduce latency for aninitial transmission of a data burst and/or for small data transfers.For example, an enhanced random access procedure may enable a WTRU tosend data before receiving a grant from the network.

In an example, a first message (e.g., eMSG1) may include a transmissionof data combined with a preamble sequence. A transmission may useresources that may be disjointed in time and/or frequency. Atransmission may use combined resources in time and/or frequency, e.g.,such that a single resource may be used for the preamble and the dataportion. For example, a preamble sequence and a data portion may be sentusing separate resources, where such resources may be associated witheach other. Sending the preamble sequence and the data portion usingseparate resources may be considered as separate transmissions. Asanother example, a preamble sequence may be added (e.g., prepended) to adata portion. Adding the preamble sequence to the data portion may beconsidered to be a single transmission. HARQ may be applicable to thedata portion of a transmission. For example, an enhanced random accessprocedure may support retransmission of the first message,retransmission of the preamble only (e.g., as a fallback to the legacyRACH procedure), and/or retransmission of the data portion only (e.g.,using HARQ).

In an example, a second message (e.g., eMSG2) may include a response tothe first message. A response to the first message may include, forexample, a Timing Advance Command (TAC) and/or HARQ feedback for thedata portion, for one or more grant(s) for retransmission of the dataportion, and/or for a new transmission.

In an example, an enhanced random access procedure may enable lowlatency access for an unsynchronized WTRU, for example, when databecomes available in the unsynchronized WTRU (e.g., uplink data arrivaland/or control plane signaling) and/or when a WTRU may receive downlinkcontrol information that may indicate the WTRU should initiate anenhanced random access (e.g., downlink data arrival).

FIG. 6 is an example of an enhanced random access channel (eRACH)procedure 600. At 602, a WTRU may have data to be transmitted. At 604,the WTRU may select a preamble 622 from a group 620 of preambles. At606, the WTRU may determine data transmission resources and/orparameters based on the selected preamble 622. At 608, the WTRU may sendthe preamble 622 on one or more PRACH resources. At 610, the WTRU maysend data (e.g., via a shortened UL transmission 640) on the determineddata transmission resources. At 612, the WTRU may receive a RAR from thenetwork. If the WTRU does not receive a RAR from the network, the WTRUmay repeat 604, 606, 608, and 610. If the WTRU receives a NACK with agrant, the WTRU may retransmit the data, at 614.

A WTRU may initiate an eRACH procedure 600. A network may initiate aneRACH procedure 600 using, for example, eMSG0 (e.g., NR-PDCCH order orL3/RRC). Message eMSG0 may include control information.

A WTRU may initiate an eRACH procedure, for example, in response to oneor more of the following events: (i) a WTRU-dedicated network (NW)order, (ii) a dynamic scheduling of CB-eRACH resources, e.g., combinedwith WTRU-autonomous triggers and/or (iii) L3/RRC (or MAC CE)network-controlled mobility.

A WTRU may initiate an eRACH procedure, for example, in response to aWTRU-dedicated NW order, such as upon reception of downlink controlsignaling (e.g., a DCI on NR-PDCCH) that may include an indicationand/or a request for a WTRU to perform such eRACH procedure. Thedownlink control signaling may include one or more WTRU-dedicated eRACHparameters to be used in the eRACH procedure.

A WTRU may initiate an eRACH procedure, for example, in response to adynamic scheduling of CB-eRACH resources. For example, the WTRU mayinitiate an eRACH procedure in response to scheduling of CB-eRACHresources if the WTRU also detects one or more WTRU-autonomous triggers.An example of a WTRU-autonomous trigger may include reception ofdownlink control signaling (e.g. a DCI on NR-PDCCH). The downlinkcontrol signaling may include scheduling information for transmission ofa first message of the eRACH procedure (e.g., eMSG1) and a trigger suchas a WTRU-autonomous trigger. The downlink control signaling may includeone or more eRACH parameters for a contention-based access. DCI may bescrambled with an RNTI that may be shared by a plurality of WTRUs, e.g.,including a “cell/system”-specific RNTI for eRACH.

A WTRU may initiate an eRACH procedure, for example, in response toL3/RRC (or MAC CE) network-controlled mobility, such as upon receptionof L3/RRC control signaling (or MAC CE) that may include areconfiguration with a mobility event. The L3/RRC may include one ormore dedicated eRACH parameters.

Control information (e.g., in eMSG0) may include, for example, one ormore of the following: (i) a resource indicator, (ii) a preamble index,(iii) power control information TPC, and/or (iv) a grant.

A resource indicator (e.g., in a DCI and/or RRC message) may, forexample, correspond to a resource block assignment. A resource indicatormay be associated with the data portion (e.g., and not a control portionand/or preamble portion). A resource indicator may be associated withthe preamble transmission only (e.g., contention-free randomaccess—CFRA). A WTRU may determine a resource allocation for the dataportion as a function of the resource assignment of the preamble. A WTRUmay (e.g., alternatively) determine a resource allocation for thepreamble and the data portion, for example, when a joint resource isused or when the WTRU may determine separate resources (e.g., from anindex in a table or similar).

DCI may be received on NR-PDCCH or another similar channel. One or moreresources may be dedicated (e.g., contention-free) to a specific WTRU.For example, one or more resources may be dedicated to a specific WTRUwhen the DCI is received using C-RNTI or equivalent. One or moreresource(s) may (e.g., alternatively) be shared (e.g., contention-based)and may be accessible to a plurality of WTRUs (e.g., when scrambledusing a shared RNTI such as CB-eRACH-RNTI.

A Preamble index (e.g., in a DCI and/or an RRC message) may, forexample, indicate a specific preamble sequence (e.g., for dedicatedsignaling). A preamble index may indicate a specific preamble groupand/or range (e.g., for shared signaling).

Power Control information (e.g., such as transmit power control (TPC))may be included in a DCI and/or an RRC message. The power controlinformation may be applicable to preamble transmission on ePRACH, forthe data portion, one for each or one for both.

A grant (e.g. in a DCI and/or RRC message) may be received (e.g. incontrol signaling) by a WTRU. The grant may be associated with thetransmission of eMSG1. The grant may be for the transmission of eMSG1.The grant may (e.g. alternatively) be for the transmission of a dataportion of eMSG1. Preamble transmission may be performed according toother information received in the control signaling, such as accordingto other parameters, e.g., as described herein. For example, aWTRU-dedicated grant may be indicated (e.g. for dedicated signaling) ora contention-based grant (e.g. for shared signaling).

In an example of network (NW)-controlled contention a WTRU may have oneor more autonomous triggers. For example, a WTRU may determine that ithas data available for transmission. The data transmission may beapplicable to an eRACH procedure. The WTRU may decode a downlink controlchannel, for example, using a shared RNTI (e.g. CB-eRACH-RNTI). The WTRUmay decode a DCI that may include dynamically scheduled system-specificePRACH parameters (e.g. and an associated grant and/or set of PRBs forthe data portion). The WTRU may initiate a transmission of a preamble,e.g., using the determined ePRACH resources, and a transmission of thedata portion, e.g., using the received grant and/or subset of PRB(s).

The WTRU may determine from control signaling whether it should performthe eRACH procedure according to contention-free or contention-basedprinciples.

A WTRU may initiate an eRACH procedure, for example, to perform initialaccess, to request transmission resources (e.g. a scheduling requestsuch as eRA-SR), to transmit an amount of data (e.g. based on athreshold), to perform WTRU-autonomous mobility, a scheduling request orbased on network order. A WTRU may (e.g. as part of the procedure)select the procedure (e.g. legacy RACH versus eRACH), for example, basedon service, DRB, type of accesses currently available to the WTRU, etc.The WTRU may determine whether to select a legacy RACH procedure or aneRACH procedure based on a type of uplink data to be transmitted and/orthe purpose of the random access request. For example, the WTRU mayselect the legacy RACH procedure for type 2 data. Type 2 data mayinclude enhanced mobile broadband (eMBB) data, for example. As anotherexample, the WTRU may select the eRACH procedure for type 1 data. Type 1data may include ultra-reliable and low latency communications (URLLC)data, for example.

A WTRU may select an eRACH procedure. A WTRU may select a preamblesequence, e.g., in addition to resources for preamble and data. Theresources used for a preamble and the resources used for data may havesome association, such as an implicit association. A WTRU may determinewhich data (if any) may be transmitted in the data resources and maydetermine applicable PHY/MAC control information to be transmitted, forexample based on the preamble that was used.

A WTRU may trigger the PHY layer to transmit the preamble on selectedresources for preamble transmission and may send control information andany data to the PHY layer for transmission on the selected dataresources.

A WTRU may (e.g. following preamble and data transmission) performmonitoring of the control channel for detection of eRAR. A WTRU mayperform DRX (e.g. DRX for control channel monitoring) for a period oftime prior to a specific eRAR expected reception time or time window.

An eRACH procedure may be triggered. A WTRU may initiate an eRACHprocedure, for example, as a consequence of one or more of the followingevents: (i) The WTRU determines that is has data available fortransmission; (ii) the WTRU determines that it should performWTRU-autonomous mobility and/or (iii) the WTRU determines that it shouldperform a reconfiguration of a L1/PHY aspect and/or a Uu interface.

A WTRU may determine that is has data available for transmission. Forexample, this may correspond to one or more of the following events: (i)initial access of a WTRU to a cell or TRP (e.g. the WTRU may make afirst transmission to a cell or TRP while in an IDLE state or state ofnon-communication); (ii) initiation of a new service or logical channeland/or (iii) arrival of data at the WTRU.

A WTRU may determine that it should perform WTRU-autonomous mobility.For example, this may correspond to a transition/handover from onecell/TRP to another cell/TRP.

A WTRU may determine that it should perform a reconfiguration of aL1/PHY aspect and/or a Uu. For example, this may correspond to one ormore of the following events: (i) creation/use/addition of a new beamand/or (ii) addition of a cell/TRP to the WTRU's set of activecells/TRPs.

A WTRU may make a determination, for example, (e.g. only) when it doesnot have valid uplink timing alignment.

A WTRU may determine that it should initiate a RACH procedure while italready has an ongoing eRACH procedure. In an example, the WTRU mayperform one or more of the following:

A WTRU may continue with the ongoing eRACH procedure (e.g. unless thetrigger to initiate the RACH procedure may be due to a mobility eventthat may invalidate the current resources used for the ongoing eRACHprocedure) to a recovery procedure that may be related to the executionof the ongoing eRACH procedure (e.g. due to a failure case such asmaximum number of eMSG1 transmissions, failure to detect/measureapplicable reference signal, loss of downlink synchronization or thelike) or to any other impairment to the ongoing eRACH procedure. A WTRUmay refrain from initiating the RACH procedure (e.g. eRACH may beprioritized when ongoing and when fulfilling a similar purpose).

A WTRU may (e.g. otherwise) initiate a RACH procedure. A WTRU maycontinue with an ongoing eRACH procedure (e.g. both procedures may runin parallel such as when fulfilling different purposes). Both proceduresmay run in parallel, for example, when new data becomes available fortransmission that may be associated with or applicable to a SRB, a DRB,a numerology (e.g. a type of SOM), a numerology block (e.g. a SOM), aTrCH or similar and that may otherwise not have triggered a proceduresimilar and/or corresponding to the ongoing eRACH and/or its resources.

A WTRU may determine that it should initiate an eRACH procedure while itmay already have an ongoing RACH procedure. A WTRU may perform one ormore of the following:

A WTRU may continue with the ongoing RACH procedure, for example, whenthe determination to initiate an eRACH procedure may not be (e.g.directly) related to criteria (or type thereof) that triggered theongoing RACH procedure. For example, this may include new data that maybecome available for transmission, may be associated with or applicableto an SRB, a DRB, a numerology (e.g. a type of SOM), a numerology block(e.g. a SOM), a TrCH or similar and may otherwise not have triggered aprocedure similar and/or corresponding to the ongoing RACH and/or itsresources.

A WTRU may (e.g. otherwise) prioritize and initiate the eRACH procedure.The WTRU may cancel the ongoing RACH procedure, for example uponinitiating the eRACH procedure.

A WTRU may determine that it should initiate a second eRACH procedurewhile it has a first ongoing eRACH procedure. In this case, the WTRU mayperform one or more of the following:

A WTRU may continue with the first ongoing eRACH procedure, for example,when the determination to initiate a second eRACH procedure may berelated or similar to a criteria (or type thereof) that triggered thefirst instance of the eRACH procedure (e.g. an event that may trigger aneRACH procedure corresponding to the same set of eRACH resourcesutilized by the first instance of the eRACH procedure). An event mayinclude new data that may become available for transmission, may beassociated with and/or applicable to an SRB, a DRB, a numerology (e.g. atype of SOM), a numerology block (e.g. a SOM), a TrCH or similar thatmay be associated with such eRACH resources. Different beam processesassociated with the same specific reference signal (e.g. correspondingto the same TRP) may be considered the same resource unless the triggermay be related to beam management.

A WTRU may (e.g. otherwise) initiate a second instance of the eRACHprocedure.

A set of eRACH resource(s) may include one or more of a set ofpreambles, preamble resources, data resources/association, transmissionfrequency, etc.

A WTRU may determine an applicable RACH procedure, e.g., legacy RACH oreRACH procedure. A WTRU may initiate a random access. The WTRU maydetermine that it should perform a random access procedure. The WTRU may(e.g. further) determine that a plurality of such access procedures maybe used (e.g. a legacy RACH or a eRACH procedure). The WTRU maydetermine whether to select, for the random access, a first RACHprocedure or a second RACH procedure. The first RACH procedure may be alegacy RACH procedure and/or a 4-step RACH procedure. For example, alegacy RACH procedure may include four steps. The second RACH proceduremay be an eRACH procedure and/or a 2-step RACH procedure. For example,an eRACH procedure may include two steps.

When the WTRU selects the second RACH procedure, the WTRU may determineat least one PRACH resource associated with the second RACH procedure.The WTRU may determine a preamble sequence associated with the secondRACH procedure. The WTRU may determine a data resource for uplink data,for example, based on the at least one PRACH resource, the preamblesequence, a type of uplink data, and/or a size of uplink data. The WTRUmay send a RACH transmission to a network device using the at least onePRACH resource and the data resource. The RACH transmission may includethe preamble sequence and the uplink data.

A WTRU may determine to perform an eRACH procedure according to one ormore factors. Several examples are provided below.

A WTRU may determine to perform an eRACH procedure, for example, basedon its connectivity state (e.g. IDLE, CONNECTED, “light connected”). Adetermination may be made in combination with other conditions.Conditions for selection may be different, for example, depending on aWTRU's connectivity state.

A WTRU may determine to perform an eRACH procedure, for example, basedon a specific trigger received for initiation of the procedure.

A WTRU may determine to perform an eRACH procedure, for example, basedon its (e.g. current) timing alignment status or specific timingalignment criteria or whether it may be allowed to transmit preamblecombined with data. A WTRU may be allowed to transmit preamble combinedwith data, for example, when the time since its last UL transmission, orthe time since last reception of a timing advance command may not exceeda predefined or network-provided threshold. A WTRU may (e.g.alternatively or additionally) make a determination based on a cell-sizeprovided by the network. In an example, a WTRU may be allowed to performtransmission of preamble combined with data or use a different set ofthresholds for comparison of its timing alignment status when makingsuch determination, for example, when cell size may be less than apre-defined or configured threshold.

A WTRU may determine to perform an eRACH procedure, for example, basedon a network configuration, which may be provided in system information.A determination may be made whether a 2-step or 4-step procedure shouldbe used. Network configuration information may be provided in broadcastsystem information (e.g. SIB) and may indicate which RACH procedure tobe used. Such information may also indicate or be used to determineadditional behavior of a WTRU during the RACH procedure. In an example,a 2-step approach may be applied and the WTRU may not expect a TAC ineMSG2, for example, in small cells where TA may not be required.

A WTRU may determine to perform an eRACH procedure, for example, basedon amount/duration of data transmission. A WTRU may determine that itcan transmit preamble combined with data, for example, when a desireddata transmission may not exceed a pre-defined or configured amount orwhen the transport block duration does not exceed a pre-defined orconfigured duration. A data amount may be based on an amount of datathat may be available for transmission and/or an amount of data bufferedby a WTRU for one or more specific logical channels/services or on theduration of a transport block that may be required to transmit a pendingtransmission or message.

A WTRU may determine to perform an eRACH procedure, for example, basedon the type of data/transmission. For example, a WTRU may determine thatit should perform an eRACH procedure based on a property associated withthe data to transmit or the type of transmission to be made. A WTRU maymake a determination for (e.g. only) a specific logical channel or aspecific type of message (e.g. RRC control message). A WTRU may make adetermination based on transmission time-requirements associated withthe data, such as an expired time for successful transmission for data.

A WTRU may (e.g. further) be configured with a set of logical channelsor equivalent that a WTRU may select to transmit data, e.g., using theeRACH procedure. A WTRU may distinguish or determine whether the type ofdata to be transmitted meets the criteria for an eRACH based on one ormore of the following: (i) applicable service type and/or correspondingQoS associated with the data/access; (ii) bearer configuration and/or(iii) the type of and/or identity of a radio bearer (e.g. SRB or DRB)for which the data may (e.g. is to) be transmitted.

In an example, e.g., upon bearer establishment, a bearer may indicatewhether it allows for transmission in an inactive state and/or datatransmission using an eRACH procedure.

In an example, a WTRU may be configured by a network to perform datatransmissions, for example, using an eRACH procedure (e.g. only) forcertain radio bearers. A WTRU may (e.g. also) receive a configuration,for example, based on a previous request. In an example, a WTRU may movefrom a connected state to an inactive state. The WTRU may request whichbearers may be allowed for data transmission, e.g., using an eRACHprocedure.

In an example, a WTRU may be placed in an inactive state and may beprovided with a new bearer (e.g. by a network) for transmission while inthe inactive state. A WTRU may (e.g. also) be provided with the rules tomap specific application-layer data arriving at the WTRU to the bearerwhile it may be in the inactive state. A WTRU may perform an eRACHprocedure upon arrival of data to that specific bearer. A WTRU mayperform a legacy RACH procedure, for example, when data arrives foranother bearer.

A WTRU may determine to perform an eRACH procedure, for example, basedon an observed data rate. A WTRU may make a determination based on theobserved data rate (e.g. frequency of packet arrival) at the WTRU. AWTRU may compare an observed data rate to a configured threshold ratefor performing eRACH (e.g., 2-step rather than 4-step procedures).Determinations may be made for a specific logical channel or radiobearer.

A WTRU may determine to perform an eRACH procedure, for example, as aresult of a timer expiring. For example, a WTRU may be configured totransmit a preamble combined with a data transmission at least every (x)seconds. A WTRU may (e.g. upon timer expiration) perform a transmissionregardless of the presence of data for transmission at the expiration ofthe timer (e.g. by transmitting a BSR or other control information whenno other data is present or leaving the data resources empty). This mayallow a WTRU to maintain a certain level of timing alignment (e.g. roughtiming alignment) so that it may continue to use eRACH (e.g., a two-stepapproach) and/or limit the length of a guard period when using eRACH(e.g., a two-step approach).

A WTRU may determine to perform an eRACH procedure, for example, basedon a synchronization signal (e.g. the presence or property of asynchronization signal from which PRACH resource or PRACH sequence maybe derived). A WTRU may use information about a synchronization sequenceto make a determination, such as one or more of: (i) frequency band andassociated type of access, (ii) sequence property, and/or (iii) presenceof a second signature sequence.

In an example of using a frequency band and associated type of access, aWTRU may determine that the presence of a synchronization signal on aspecific frequency may be associated with use of an eRACH procedure(e.g. licensed versus unlicensed).

In an example of using a sequence property, a WTRU may determine that anindex associated with the synchronization signal may indicate to performan eRACH procedure. An index may, for example, be associated with a beamindex.

In an example of using a presence of a second signature sequence, a WTRUmay determine that the presence of a second signature sequence, whichmay be related to the first sequence and may have a specific sequenceproperty, may indicate performance of the eRACH procedure.

A WTRU may determine to perform an eRACH procedure, for example, basedon whether the WTRU is configured with C-RNTI. For example, the WTRU mayinitiate an eRACH procedure when it is configured with a C-RNTI.

A WTRU may use a (e.g., alternative) selection procedure fordetermination of the procedure, for example, when the WTRU may detect asynchronization signal for RACH procedure and a synchronization signalfor an eRACH procedure. A WTRU may determine an applicable RACHprocedure, e.g., legacy or eRACH procedure, for example, based on one ormore factors. Several examples are provided below.

A WTRU may determine an applicable RACH procedure, e.g., legacy RACH oreRACH procedure, for example, based on a measured channel occupancy. AWTRU may make measurements of channel occupancy and may choose totransmit a preamble combined with data, for example, when the measuredchannel occupancy may be larger than (or less than) a defined orconfigured threshold. A determination may support unlicenseddeployments, where access to the channel may be maintained in situationsof high load, for example, by transmitting a preamble combined with data(e.g. as opposed to an LIE-like RA procedure with four independentchannel access procedures).

A WTRU may determine an applicable RACH procedure, e.g., legacy RACH oreRACH procedure, for example, based on estimated path loss and channelconditions. A WTRU may make measurements of path loss or channel basedon reference signals and may determine whether to use 2-step vs 4-step,for example, depending on whether an estimated path loss may be below orabove a certain threshold. In an example, a WTRU may select a 2-stepprocedure, for example, when the path loss may be below a threshold. Athreshold may be broadcast by a network. A threshold may depend on thefrequency band. This may allow a WTRU to estimate a distance to acell/TRP and determine whether to use 2-step procedure, e.g., when theWTRU may be within a certain distance to the cell/TRP.

A WTRU may determine an applicable RACH procedure, e.g., legacy RACH oreRACH procedure, for example, based on a sync sequence index. A syncsequence index may convey information about a sync sequence transmitpower and/or TRP power class, for example, so the WTRU can estimate pathloss without receiving further system information. This may be useful,for example, when “PRACH” may be transmitted after synchronization.

A WTRU may determine an applicable RACH procedure, e.g., legacy RACH oreRACH procedure, for example, based on a Target TRP. A WTRU maydetermine to use a eRACH procedure, for example, when a target TRP maybelong to the same TRP group most recently used by the WTRU (e.g. withina configurable time period). For example, a WTRU may have sparse andbursty communication to a

TRP interspersed with long periods of inactivity. This may enable a WTRUto reuse pre-configured parameters to enable efficient eRACH. In anexample, a WTRU may perform a legacy RACH, for example, upon expirationof a timer, e.g., regardless whether an intended target of a randomaccess procedure is the same or is from the same TRP group.

A WTRU may determine an applicable RACH procedure, e.g., legacy RACH oreRACH procedure, for example, based on a response from a network. A WTRUmay determine, (e.g. based on a network response in a previouslyperformed eRACH procedure or a related message) that further accesses ordata transmissions may be made using a legacy RACH procedure. In anexample, a WTRU may perform an eRACH procedure where the network mayrespond with an indication (e.g. implicit or explicit) to retry, forexample, using a legacy RACH procedure. An indication may be associatedwith a backoff indication.

A WTRU may decide to perform an eRACH procedure, for example, to allowdata transmission while remaining in an inactive state. Conditions forselecting an eRACH procedure may (e.g. also) be applicable to a WTRUdeciding to perform data transmissions while remaining in a new state. AWTRU may be configured with conditions for which it may remain in theinactive state while performing data transmission (e.g. as describedabove). A WTRU may select an eRACH procedure as a result of theconditions.

A WTRU may (e.g. alternatively) perform an eRACH procedure for datatransmission in the inactive state or to transition to RRC CONNECTED. AWTRU may indicate (e.g. implicitly or explicitly as part of the preambleor data transmission) in the eRACH procedure whether to transition toRRC CONNECTED or remain in the inactive state.

A WTRU may receive a message that indicates a network order to performan eRACH procedure. For example, Enhanced message 0 (eMSG0) may providethe network order. A WTRU may determine to transmit eMSG1 and/orinitiate an eRACH procedure, for example, upon reception of DL signalingfrom a network. In an example, DL signaling may be received from thenetwork via downlink control information (DCI) on a control channel.

An eRACH procedure may be triggered. A WTRU may determine that a DCI mayindicate that the WTRU should initiate a random access procedure. Forexample, the WTRU may determine that the DCI indicates a random accessprocedure based on one or more of: time of reception, frequency ofreception, type of control channel, explicit indication, RNTI, WTRUoperating mode, inclusion of UL preamble resources and/or inclusion ofUL data resources.

In an example of time of reception, a DCI may be received in a timeinstant (e.g., subframe, slot, mini-slot, etc.) associated with aspecific procedure where the concerned reception time instantcorresponds to an eRACH procedure. For example, a specific slot in eachframe may be reserved for reception of a DCI that may indicate that theWTRU should initiate a random access procedure.

In an example of frequency of reception, a DCI may be received on afrequency resource (e.g. specific CCE, resource block, frequency band,carrier, etc.) that may be associated with a specific procedure, wherethe concerned frequency resource may correspond to (e.g., or indicate)the RACH or eRACH procedure.

In an example of type of control channel, a DCI may be received on acontrol channel, a set of CCEs, a numerology block, a search space,and/or using a specific numerology associated with a specific procedure,where the concerned aspects may correspond to initiation of an eRACHprocedure.

In an example of explicit indication, a DCI may include an indication ofthe type of procedure (e.g. RACH or eRACH). The WTRU may receive aneRACH indication. An eRACH indication may be, for example, one or moreexplicit flags or fields in a DCI, in the DCI format or a combinationthereof.

In an example of RNTI, a DCI may be encoded with an RNTI associated witha specific procedure (e.g. RACH or eRACH). The RNTI may correspond toinitiation of an eRACH procedure.

In an example of a WTRU operating mode, a WTRU may be in an operatingmode associated with performing a certain procedure upon reception of atrigger. The operating mode and/or the trigger may correspond toinitiation of an eRACH procedure. Triggers may correspond to anycombination of other determination procedures (e.g. explicitindication). A WTRU may have been placed in a mode based on reception ofDL signaling. For example, a WTRU may receive an RRC message which mayplace the WTRU in a mode of operation associated with reception ofeMSG0. A WTRU may (e.g. in this mode) may interpret the reception of aDCI (e.g. which may have one or more additional conditions forassociation with eRACH initiation) as an eMSG0.

In an example of inclusion of UL preamble resources, a DCI may includeone or more UL preamble resources (e.g. preamble range, preamble set,preamble value, PRB indicator for preamble transmission, etc.). A WTRUmay determine that the UL preamble resources may be associated with aspecific procedure (e.g. RACH or eRACH). The UL preamble resources maycorrespond to resources for an eRACH procedure.

In an example of inclusion of UL data resources, a DCI may includeuplink data resources (e.g. a PRB indicator for the data portion,numerology block for a data portion, or the like). A WTRU may determinethat the resources may be (e.g. are) associated with an eRACH procedure.

A WTRU may initiate (e.g., start) an eRACH procedure, for example, upontransmission of eMSG1. eMSG1 may include a preamble and data. Thestarting time for an eRACH procedure may be determined by a WTRU, forexample, based on signaling within a DCI and/or additionalsignaling/rules.

In an example, a WTRU may determine a time of transmission for apreamble following reception of eMSG0, for example, based on informationreceived in a DCI message and/or based on a fixed timing relationship.For example, a fixed timing relationship may be represented as n+x,where n may be a time of reception of the DCI and x may be an offset intime. An offset may be a fixed offset or may be provided to the WTRU,e.g., through system information or dedicated signaling (e.g. RRC, MAC,or same/another DCI). In an (e.g. alternative or additional) example,which may be used in combination with another determination, a WTRU maydetermine a time of transmission for a preamble, for example, based on aspecific time associated with a preamble resource to be used. Forexample, a WTRU may determine that an eRACH procedure may be started atthe next occurrence of a PRACH resource (e.g. when such resources may bepredefined or indicated by signaling prior to or during reception of aDCI), for example, following reception of a DCI or following a timeoffset after reception of the DCI.

A DCI (e.g. its contents) may contain the information, which may be usedby a WTRU during the performance of a eRACH procedure. Information maycomprise, for example, one or more of the following: (i) transmissionproperties of a preamble, such as numerology, preamble sequence, code,transmit power, etc.; (ii) transmission properties of data, such as MCS,scrambling code/pattern, transmit power, etc.; (iii) resources to usefor preamble sequence; (iv) resources for a data part; (v) associationrules between preamble resources and data resources, such as an index toa table of predefined association rules, a time and/or frequency offsetbetween them or other parameters that may define an association ruleand/or (vi) properties associated with retransmission, such asretransmission delay, power ramping, maximum number of HARQretransmissions, HARQ process number, etc.

An enhanced message 1 (eMSG1) may be provided. In an example, a WTRU maytransmit data combined with a preamble sequence that may be disjointedin time/frequency or combined with a preamble (e.g. prepending apreamble sequence to a data transmission).

In an example, a preamble and a data portion of one or moretransmissions may be tied using an association.

A relationship between preamble and data may be in a time domain. Forexample, a start time of a transmission of a preamble and a start timeof a transmission of a data portion may be offset from each other by aspecific amount of time. A start time may correspond to a first symbolof a slot, mini-slot, a subframe or to a specific symbol thereof (e.g.first symbol of a corresponding PRB region that may, for example, not bededicated to control signaling). A relationship (e.g. offset) may beequal to zero, for example, when transmission of a preamble and a dataportion may be continuous in time. This may, for example, facilitateblind decoding of data in a receiving node from a priori knowledge oftiming of a transmission of a data portion, e.g., as may be indicated bya preamble.

A relationship between preamble and data may be in a frequency domain.For example, a first PRB of a transmission of a preamble and a first PRBof a transmission of a data portion may be offset from each other by aspecific amount of PRBs. An offset may be equal to zero, for example,when there may be joint transmission of the preamble and of the dataportion. An association may be valid for a given transmission timeduration (or for a specific overlap in time of the respectivetransmission duration), for example, for a given slot, mini-slot,subframe or to a specific symbol thereof (e.g. one or more symbols ofresources that may, for example, not be used for dedicated to controlsignaling). An association may (e.g. alternatively) be applicable overnon-overlapping (e.g. disjointed in time) time intervals, for example,in combination with another procedure. This may, for example, facilitateblind decoding of data in a receiving node from a priori knowledge of afirst PRB of a transmission of a data portion, e.g., as may be indicatedby a preamble.

A WTRU may determine an offset in time/frequency, for example, using oneor more (e.g. a combination) of the following procedures: (i) fixed orpredefined (e.g. configured in the WTRU and assumed for at WTRUs); (ii)provided in system information (e.g. through broadcast on SIBs orprovided in an access table); (iii) based on explicit indication (e.g.explicitly indicated in DCI, or in a downlink control message such asMAC CE or RRC); (iv) based on a selected preamble (e.g. a preamble maybe associated with a specific offset to be used, where an associationmay be fixed or configured by a network); (v) based on a selected PRACHresource (e.g. a PRACH resource may be associated with a specific offsetto be used, where an association may be fixed or configured by anetwork) and/or (vi) random selection (e.g. a WTRU may select from anumber of possible offsets that may be determined to be usable by theWTRU).

For example, a WTRU may select a resource for data to occur in a firstavailable UL resource for transmission of data following transmission ofthe preamble. Resources may be provided to a WTRU through networksignaling. PRBs selected by a WTRU to transmit data may be (e.g.further) randomly selected by a WTRU. A WTRU may be limited to choosinga fixed number of PRBs for a data transmission.

A relationship between preamble and data may be in alength/size/duration of transmission. For example, the number ofresource blocks or the transport block size of a transmission of a WTRUmay be associated with properties of the preamble, such as the preamblesequence, preamble length or preamble resources. An association may bepredefined or provided by network configuration.

A relationship between preamble and data may be in encoding/scramblingof data. Encoding, scrambling or CRC for data may be associated withproperties of the preamble. For example, a WTRU may apply a CRC usingall or part of the preamble sequence. A WTRU may (e.g. also) modify aCRC, for example, based on resources selected for a preamble. In anexample, a WTRU may determine to use a part of a preamble as a CRC, forexample, when it transmits the preamble, e.g., using a first range ofresources, when it determines to use another part of the preamble as theCRC or when it transmits the preamble using a second range of resources.

A relationship between preamble and data may be in numerology. Forexample, a WTRU may use a numerology for transmission of data that maybe related to properties of the preamble, such as the preamble sequence,the resources selected for the preamble, the numerology of the preamble,etc. A WTRU rosy transmit data, for example, using the same numerologyas the preamble. A numerology of the preamble sequence may (e.g.alternatively) be the same (e.g. a reference numerology). A WTRU mayselect the numerology of a data portion, for example, based on atime/frequency location of preamble resources (e.g. specifictime-frequency locations associated with a certain numerology) or apreamble sequence (e.g. specific preamble sequences associated with acertain numerology).

A relationship between preamble and data may be in a multiple accessscheme or configuration. In an example, a WTRU may select a multipleaccess scheme (e.g. FDMA, TDMA, CDMA), and configuration parameters(e.g. specific resource elements, scrambling code, randomizationparameters) for data transmission, for example, based on properties ofthe preamble (e.g. sequence, selected resources). For example, a WTRUmay select specific resource elements or symbols within resource blocksfor transmission of data (e.g. contention-based resources) based on apreamble sequence.

A relationship between preamble and data may be in transmit power. Forexample, a maximum transmit power for data transmission may be relatedto a preamble maximum transmit power, preamble sequence, preambleresources or other properties of the preamble. A data transmit power maybe a scalar function of preamble transmit power. A function may bepreconfigured or configured in a WTRU by a network. A transmit power ofa preamble may be determined, for example, by preconfiguration ornetwork configuration and may be changed (e.g. by a specific amount)following retransmissions of the preamble.

A network configuration may be provided.

A per-bearer configuration of an eRACH procedure may be provided. A WTRUmay be configured (e.g. in RRC) on a per-bearer basis, for example, toindicate whether it is allowed to use an eRACH procedure to transmitdata. An eRACH procedure may be used for transmission while remaining inan inactive state. A configuration may determine whether a specificbearer may (e.g. would) allow a WTRU to perform data transmission whilein an inactive state or whether a WTRU in the inactive state may (e.g.would) transition to RRC CONNECTED to transmit data associated with thebearer.

A bearer configuration may (e.g. also) contain additional configurationfor an eRACH procedure. A WTRU may determine one or more of thefollowing from a bearer configuration: (i) whether eRACH may be (e.g.is) allowed for transmission of data or whether legacy RACH, and/ortransition to RRC CONNECTED may be allowed (e.g. required); (ii) thenumber of allowable retransmissions (e.g. retries) using an eRACHprocedure before fallback to legacy RACH or before transition to RRCCONNECTED; (iii) indication of a preamble or preamble group to use forpreamble transmission; (iv) parameters controlling linkage betweenpreamble and data in an eRACH procedure; (v) resource or subset ofresources to be used for preamble and/or data transmission; (vi) maximumdata transmission size that may be used while performing eRACH or whileremaining in an inactive state; (vii) maximum data rate that may be usedwhile performing eRACH, or while remaining in an inactive state; (viii)minimum time between data transmissions using an eRACH procedureallowable for a radio bearer; (ix) configuration of WTRU behavior (e.g.in case of backoff indication from eRAR) and/or (x) whethermultiplexing, segmentation and/or concatenation may be allowed for thebearer, which may include associated parameters restricting suchoperation.

In an example of transmission size, a WTRU may decide to use an eRACHprocedure, for example, when the amount of data buffered for the bearermay be below a maximum configured data size. A WTRU may (e.g. otherwise)decide to use a legacy RACH procedure or an eRACH procedure and mayindicate an intention to move to RRC CONNECTED.

In an example of data rate, a WTRU may decide to use an eRACH procedure,for example, when the rate at which data arrives for a bearer may bebelow a maximum configured rate. A WTRU may (e.g. otherwise) decide touse the legacy RACH procedure or an eRACH procedure and indicate anintention to move to RRC CONNECTED.

In an example of configuration for a backoff indication, a WTRU may(e.g. based on such configuration) may be allowed to retry a 2-stepprocedure, for example, immediately, after a configurable backoff periodor may perform data transmission by starting with a 4-step procedure,which may be determined by the configuration of the bearer for which thedata was available.

A new/dedicated bearer may be provided for data transmission in aninactive state.

A WTRU may perform data transmission using an eRACH procedure (e.g.only) for a single dedicated bearer. For example, a dedicated bearer mayhave been established during a transition from RRC CONNECTED state toinactive state.

A WTRU may be configured with a policy for mapping data packets from anapplication layer to a dedicated bearer (e.g. as opposed to an initiallyassociated bearer created for RRC CONNECTED operation) while the WTRUmay be in an inactive state. A policy may comprise, for example, mappingone or a set of TFTs to the new bearer or mapping one or a set of QoSflow identifiers from the network to the new bearer.

A WTRU may determine one or more configuration parameters associatedwith a configuration of an eRACH procedure (e.g. as described above)from the bearer configuration.

A WTRU may determine (e.g., select) a preamble (e.g., a preamblesequence). A WTRU may select a preamble, for example, based on a (e.g.required) PRACH and/or data reception reliability. For example, one ormore preambles (e.g. potentially with data) may be spread over time,frequency, spatial resources, and/or code resources. In an example, apreamble and (e.g. optionally) data may be repeated over multipleresources. A WTRU may determine a required amount of diversity toachieve a (e.g. required) reliability and may (e.g. thus) select apreamble that may achieve such diversity. A diversity (e.g. number ofrepetitions) of preamble and data portions may not be the same. Forexample, diversity for PRACH reception may be greater than diversity fordata reception. This may avoid a new, full RACH procedure, for example,when data transmission fails.

A WTRU may be limited to using specific properties or a range ofproperties, e.g., as a result of selection of one or more preambles froma set of configured preambles.

A WTRU may (e.g. alternatively) append a transmission type indicator toa preamble to indicate a transmission type and/or one or moretransmission properties.

A WTRU may indicate other information based on its preamble selection.Specific transmission properties or other information, which may bereflected in the choice of preamble, may include, for example, one ormore of the following.

A preamble selection may indicate, for example, an amount of data to betransmitted, a maximum TB size, and/or a range of allowable TB sizes. AWTRU may select a preamble based on the amount of data that will betransmitted in the data part. For example, a WTRU may determine theamount of data to be transmitted, e.g., based on the size of pendingPDU, control message, IP packet, etc. or whether there may be no data tobe transmitted (e.g. preamble transmission triggered by the timer tomaintain rough timing alignment). A determination may be limited to a(e.g. only one) specific logical channel, type of data, QoS level, typeof service, etc. A WTRU may (e.g. based on the determination) selectfrom one or more preambles that may be associated with the amount ofdata or select from one or more preambles for which a resulting TB maynot exceed a maximum associated with the preamble or falls in the rangeassociated with the preamble.

Preamble selection may indicate, for example, a type of transmission ortrigger that may have caused a transmission. A WTRU may select apreamble, for example, based on the type of data or QoS requirementsthat may be associated with the data. In an example, a WTRU may selectone or more from a set of preambles, for example, when the data may beassociated with a specific service (e.g. URLLC) or when the data may beassociated with one or more or a type of logical channel or QoS markingfrom upper layers. A WTRU may select a preamble, for example, based onwhether an enhanced (e.g., two-step) or a legacy (e.g., 4-step) RA maybe performed or based on whether the WTRU was triggered to perform atwo-step transmission without data (e.g. to obtain timing alignmentonly).

A preamble selection may indicate, for example, timing requirements thatmay be associated with data transmission. A WTRU may select its preambleas a function of transmission latency requirements that may beassociated with data. A WTRU may select its preamble as a function ofthe WTRU's processing capabilities. The WTRU's processing capabilitiesmay include processing time required between reception of downlinkcontrol signaling that grant resources for an uplink transmission (e.g.in a message that includes a RAR) and/or the corresponding uplinktransmission (e.g. msg3 for a 4-step RACH procedure). A WTRU may selecta preamble as a function of a combination of the latency requirement forthe data that triggered the RACH procedure and the WTRU's capabilitiesin terms of such processing time. A WTRU may (e.g. in this case) furthertrack a time that may be required for transmission of the data and mayselect a preamble based on a current time difference with a requiredtransmission time.

A preamble selection may indicate, for example, a WTRU buffer status. AWTRU may select a preamble, for example, based on its buffer status forone or multiple logical channels, logical channel groups, data types orthe like. A preamble may be associated with a range for a buffer status.A WTRU may make a selection based on comparison with this range, in an(e.g. another) example, a WTRU may select a preamble based on whetherthe WTRU's buffer status for a logical channel may exceed an allowabletransmission size for a data part of the preamble data transmission. AWTRU may select a preamble as a function of a request for a grant in theeRAR.

A preamble selection may indicate, for example, WTRU identity. A WTRUmay select a preamble, for example, based on an identity at the WTRU. Anidentity may be preconfigured (e.g. GUTI) or provided by a network (e.g.C-RNTI or IMSI). An ID may be provided by a network, for example, duringa state transition by the WTRU (e.g. when moving from connected tolightly connected or IDLE). An ID may be entirely or may contain aportion randomly selected by the WTRU. An ID may depend on a WTRU state(e.g. IDLE, connected or light connected state).

A preamble selection may indicate, for example, a location and/ornumerology of a data transmission. A WTRU may perform selection of thetime/frequency resources and/or numerology for transmission of the data.A WTRU may select a preamble associated with a location and/ornumerology. A WTRU may determine a diversity or reliability for the dataportion and may select a preamble associated therewith. For example, apreamble may map to data resources that enable repetition overfrequency, time, space or code.

A preamble selection may indicate, for example, MCS. A WTRU may select apreamble based on an MCS it may use for transmission of associated data.

A preamble selection may indicate, for example, random selection. A WTRUmay perform random selection of a preamble from a configured set ofpreambles, or from a set of preambles that may meet one or more (e.g. acombination of) other rules for preamble association.

A preamble selection may indicate, for example, a demodulationconfiguration of a data transmission. A WTRU may select a preamble, forexample, based on a demodulation configuration of a data transmission.In an example, a preamble may be configured to be used as a demodulationreference signal (DMRS) for a data transmission. In an example, use of apreamble as a DMRS for a data transmission may reduce signaling overheadand may increase data transmission capacity. For example, a WTRU mayselect a long preamble sequence, e.g., to provide more accuratefrequency and error correction at TRP receiver. A set of referencepreamble numerology may be preconfigured for a WTRU to use, for example,when a preamble may be used for a channel estimate for datatransmission. A WTRU may match a preamble configuration with a datatransmission, e.g., including, for example, numerology, frequencyallocation, beamforming configuration, etc. A WTRU may (e.g.alternatively or additionally) select a pre-configured demodulationreference signal (DMRS) for a data transmission. A WTRU may select ashort preamble sequence at a different frequency resource allocationwithout consideration of using transmission parameters compatible withthose of the data transmission.

FIG. 7 is an example of a demodulation configuration 700. As shown inFIG. 7, the WTRU may use the preamble as a DMRS for a data transmission.The WTRU may send a DMRS before the data transmission. The WTRU may senda DMRS during the data transmission.

A preamble selection may indicate, for example, a preamble receivingnode. A WTRU may be configured or based on a downlink transmissiontransmit a preamble may have intended for a TRP or a group of TRPs. Inan example deployment, a cell may consist of a group of TRPs that maycollectively provide initial access coverage of a cell in a manner ofSFN. A WTRU may select a preamble according to a cell-specificconfiguration with properties or characteristics that may optimize RACHreception performance at (e.g. each) individual TRPs. In an example, aWTRU may select a preamble that may consist of a number of repeatedshort sequences. This may improve uplink RACH link performance, forexample, because a TRP may use receiver beamforming and may receive partor all of a short sequence in one or multiple receive beams. A TRP may(e.g. also) apply coherent combining of short sequence versions receivedin multiple receive beams. In an (e.g. another) example, a TRP may use awide receive beam. The WTRU may select different transmit beamformingconfiguration for each short sequence, e.g., to provide a beamforminggain to the preamble transmission. A WTRU may (e.g. when it may transmita preamble to a specific TRP) select a (e.g. one) long preamblesequence, e.g., to provide high energy accumulation of the preambledetection by the targeted TRP.

A preamble selection may indicate, for example, a request for transitionto RRC CONNECTED. A WTRU transmitting eRACH while in inactive state mayindicate (e.g. based on a preamble selection or associated resources),for example, whether the WTRU would like to transition to RRC CONNECTEDstate (e.g. following the eRACH procedure) or remain in inactive state(e.g. to continue to transmit data using the eRACH procedure).

A preamble selection may indicate, for example, that the amount of datato be transmitted exceeds a maximum. A WTRU may select a preamble, forexample, to indicate whether it can perform transmission of at pendingdata using the BRACH procedure. For example, an indication may allow thenetwork to provide an additional UL grant in the eRAR.

A preamble selection may indicate, for example, a request forsemi-persistent DL resources. A WTRU may indicate its preference toallocate DL resources (e.g. a finite set that may be allocated without aDL grant). Implicit allocation of DL resources may permit a network toprovide application layer ACKs, for example, when the WTRU performs datatransmission in inactive state for a prolonged period of time.

A preamble selection may indicate, for example, a number of requestedgrants. A WTRU may request additional grants from the network in theeRAR. For example, a WTRU may transmit SRB and DRB using separateresources following the transmission of eMSG2. A selected preamble mayindicate the request by the WTRU.

A preamble selection may indicate, for example, a data format. A WTRUmay indicate (e.g. as part of a preamble) a data transmission format,such as the type of MAC header used, the presence/absence of signaling(SRB), the amount of data associated with each bearer, etc. A formatindication may reduce header overhead transmitted with the data part,which may increase resource efficiency.

A WTRU may (e.g. further) receive multiple preambles from a network(e.g. through RRC signaling) and may select a provided preamble, e.g.,based on one or more properties.

In an example, which may be used in conjunction with other preambleselection, a WTRU may select its time/frequency resources for preambletransmission based on one or more rules for preamble selection. A WTRUmay learn of an association between data transmission properties, WTRUinformation and preamble resources, for example, by preconfiguration orby network configuration (e.g. broadcast or dedicated signaling and/orfrom an access table).

Physical Random Access Resource Selection, e.g., PRACH or enhanced PRACH(ePRACH) may be provided. A Procedure with the same PRACH for bothaccess procedures may be implemented. A WTRU may utilize a common set ofresources for RACH (4-step) and eRACH (2-step) transmission. A WTRU maydetermine PRACH/ePRACH resources from system information, which may beassociated with a specific synchronization sequence and/or frompreconfigured information. For example, a frequency range and/ornumerology for transmission of PRACH/ePRACH may be preconfigured in aWTRU while specific resource blocks (e.g. tune/frequency location) maybe defined by system information.

Differentiation may be based on preamble sequence. A WTRU may selectfrom a different set of preamble sequences, for example, based on thetype of procedure. A first set of preambles (e.g. preamble group C) maybe associated with ePRACH while one or more sets of preambles (e.g.preamble group A and B) may be associated with PRACH transmission.

Differentiation may be based on blind decoding of data by a network. AWTRU may (e.g. alternatively) utilize the same preambles for PRACH andePRACH. A network may determine the use of ePRACH, for example, throughthe detection of data transmitted by the WTRU. A WTRU may (e.g. always)fall back to PRACH retransmission, for example, when there is a failureto receive eMSG1

A procedure may have separate PRACH/(e)PRACH resources for each ofmultiple access procedures. A WTRU may utilize a separate set ofresources for PRACH and ePRACH. A WTRU may select resources associatedwith PRACH, for example, when it performs a legacy RACH procedure andmay select resources associated with ePRACH, for example, when itperforms a eRACH procedure

Data resources may be selected, e.g., based on a preamble. A WTRU mayselect or determine data resources (e.g. time/frequency) and/or datatransmission properties (e.g. numerology, MCS), for example, as afunction of a selected preamble and/or a function of selected preambleresources. In an example, a WTRU may be configured with a definedmapping between a preamble sequence/preamble resources and dataresources/data transmission properties.

For example, a WTRU may be provided with an overall set of usable dataresources and a defined mapping (e.g. based on a table or list) betweeneach preamble and the corresponding resource block(s) to be used. In an(e.g. another) example, resource block(s) within a provided set ofoverall resources may be indexed by a preamble sequence number orpreamble index of the selected preamble.

A WTRU may obtain its overall set of usable data resources from one ormore of the following, for example: (i) system information (e.g.broadcast or dedicated and/or on-demand), (ii) access table and/or (iii)PDCCH grant to a specific RNTI (e.g. resources may consist ofcontention-based resources provided dynamically by a network).

A WTRU may autonomously select resources, e.g., from a defined subset.For example, WTRU preamble selection may determine an allowable subsetof resources and/or transmission properties that may be usable by theWTRU. A WTRU may select from this subset of resources and/ortransmission properties based on one of more of the following: randomselection, measurements or channel occupancy, amount of data to sendand/or type of data.

In an example of random selection, a WTRU may randomly select a numberof transport blocks that may allow it to transmit a pending message.

In an example of selection based on measurements or channel occupancy, aWTRU may perform measurements (e.g. in the DL) on allowable dataresources that may be associated with a selected preamble. A WTRU mayselect resources that may have the best quality or the least channeloccupancy. A determination of measurements or channel occupancy mayconsist of RSRP measurements, achievable diversity level of a channel(e.g. number of independent diversity paths enable efficientrepetition), energy measurements, detection of occupancy by decoding ofPRACH and/or other transmissions from other WTRUs.

In an example of selection based on an amount of data to send, a WTRUmay select a number of resource blocks or the like based on the amountof data to send or data in its buffers (e.g. up to a maximum amount).

In an example of selection based on a type of data (e.g. QoS, servicetype, or logical channel), a WTRU may select its resources to associatea specific numerology (e.g. TTI) with a type of service to be used.Numerology may be associated (e.g. through signaling by a network) witha time/frequency location of a selected resource.

A WTRU may (e.g. further) provide an indication of selected resources asinformation in a preamble transmission and/or the data. A WTRU mayformat an indication, for example, as a bitmap of resource blocksselected by a WTRU for transmission.

A WTRU may include (e.g. in a data transmission or in a control regionof the data) additional information, which may comprise one or more ofthe following, for example: (i) an amount of data transmitted and/or anMCS that may be used to transmit the data; (ii) HARQ information (e.g.HARQ process number, redundancy version, retransmission number, etc.that may allow a WTRU to maintain multiple HARQ processes fortransmission (at least initially) through the procedure of preamble+datatransmission); (iii) WTRU Identity; (iv) WTRU buffer status; (v) one ormore synchronization sequence(s) (e.g. measured by WTRU); (vi) beamindex or beam parameters used or to be used by the WTRU (e.g. for futuretransmissions); (vii) desired format or desired information in the eRAR(e.g. WTRU may request a UL grant to be sent in the eRAR); (viii) QoSRequirements of the data; (ix) measurements of reference orsynchronization signals during/prior to transmission of thepreamble+data and/or (x) state transition request (e.g. from IDLE toconnected or from light connected to connected) or a request to stay inthe current state. For example a WTRU may have a short data burst andmay indicate to the network that it may not expect a MSG2 to includeanything other than a HARQ A/N (e.g. the WTRU may not receive TA commandor a grant for a future transmission and upon reception of ACK mayreturn to a non-timing-aligned mode).

Information, for example, may be included in a MAC CE or RRC messagethat may be sent with a data transmission.

A WTRU may determine an allowable MCS or an MCS to use for datatransmission, for example, based on the selected preamble. A WTRU maydetermine an MCS based on one or more (e.g. a combination) of any of thefollowing: network signaling, a property of a signature sequence orsynchronization signal, a property of a timing alignment state, apredefined table of transport format/MCS and/or an eRACH trigger.

In an example of a determination by network signaling, a WTRU mayreceive an MCS to be used for a data transmission based on broadcast ordedicated network signaling.

In an example of a determination from a property of a signature sequenceor synchronization signal, a WTRU may determine an MCS based on a signalstrength, for example, in combination with a type of signature sequencedetected by the WTRU prior to trigger of the 2-step procedure. A WTRUmay be configured with a mapping between a signature sequence typeand/or strength and a corresponding MCS.

In an example of a determination from a property of a timing alignmentstate, a WTRU may determine an MCS, for example, based on the amount oftime since the last reception of a timing advance command, from the sizeof the cell, the time of last UL transmission or combination thereof.

In an example of a determination based on a pre-defined table oftransport format/MCS, a WTRU may determine an MCS based on a predefinedor network configured table of allowable MCS. A WTRU may select fromallowable MCSs in the table. A network may perform blind decoding, forexample, to determine an MCS selected by the WTRU.

In an example of a determination based on what triggered the eRACH, aWTRU may select an MCS for data transmission, for example, usinginformation in eMSG0, e.g., when triggered by a network and usinginformation in broadcast signaling, e.g., when triggered autonomously bythe WTRU (e.g. data arrival at the WTRU).

In an example, a WTRU may receive a mapping between a selected preambleand a corresponding MCS for data transmission. A WTRU may use an MCS fordata transmission, which may be associated with the preamble. In an(e.g. another) example, preambles may have a restricted range of MCSassociated with them. A WTRU may select a specific MCS within arestricted subset, for example, based on measurements of a signaturesequence or a synchronization signal that may be performed prior toinitiation of the two-step procedure.

A WTRU may determine certain properties of the data transmission basedon presence of and information carried in a control channel. Preambleand data may be aligned with transmission of a control channel in theDL. A control channel may carry information about a data transmission,such as: (i) frequency/time/code resource allocation; (ii) numerology,(iii) MCS and/or (iv) modulation.

A WTRU may decode a control channel based on, for example, a specificgroup RNTI, e.g., to determine such properties. An RNTI may bepreconfigured in a WTRU or may be specific to a category/type of WTRU(e.g. RNTI per WTRU type) or service requested by the WTRU.

Transmission of data with lack of timing advance may cause interferenceand may make it difficult for a network to receive transmissions.

Guard periods may be selected. A WTRU may transmit its data within anallocated resource for data transmission. A guard period may be usedprior and/or after data transmission. A WTRU may select from a set ofguard period durations or guard period configurations, for example,based on its environment or timing alignment status. This may includeselecting a guard period that may correspond to or may be associatedwith one or more (e.g. a combination) of the following, for example: (i)cell size and/or WTRU speed; (ii) timing alignment status (e.g. timesince the WTRU was last time aligned) and/or (iii) WTRU measurements(e.g. for reference signal, signature sequence or synchronizationsignal).

A WTRU may make a selection from a list of configured guard periodconfigurations, which may have a predefined or configured association,e.g., as discussed above. A WTRU may (e.g. alternatively) receive itsguard period configuration from the network.

A WTRU may transmit a known sequence within a portion of a guard period.A sequence may consist of a cyclic prefix or a sequence that may berelated to (or a function of) a selected preamble. The duration of asequence may be related to a guard period configuration. For example, aduration of a sequence may be a specified fraction of a guard periodduration.

A sequence may allow a network to detect the start of transmission by aWTRU within an allocated resource.

Numerology selection may be provided. A WTRU may select a large CP for afirst PRACH transmission. A PRACH format may include CP and GP.Subcarrier spacing may be based on a downlink channel in which a RACHconfiguration may be received. This may avoid interference betweendifferent WTRU preamble transmissions, e.g., even with differentpreamble sequences.

Interference avoidance and management may be provided. Multiple WTRUsmay select an identical preamble, which may result in a preamblecollision and data transmission interference with each other, in anexample, a WTRU may bear form a step-1 transmission, e.g., to reduce acollision. A TRP may receive two identical preambles in two separatereceive beams and there may be no interference for a data part of thetransmission. A WTRU may select a step-1 transmission beamformingconfiguration, for example, based on beam sweeping, random beamselection or DL/UL channel reciprocity, e.g., using downlink receptionangle of arrival information.

Additional MAC CEs may be transmitted. A WTRU may transmit (e.g. alongwith the data transmission) one or more MAC CEs, MAC CEs may (e.g.additionally) contain information (e.g. that may be provided with thepreamble), for example, when the information has not already beenincluded with the preamble.

A WTRU may initiate a retransmission procedure (e.g. for eMSG1), forexample, upon a failed 2-step access or failed data transmission. Aretransmission may be triggered, for example, by one or more of thefollowing events: (i) a WTRU may not receive a valid eRAR over a definedor expected period of time; (ii) a WTRU may receive an eRAR with a WTRUID that may not match the WTRU's own ID; (iii) a WTRU may receive aneRAR intended for it with a HARQ process state corresponding to NACKand/or (iv) a WTRU may receive an eRAR intended for it with a HARQprocess state corresponding to ACK but an NDI indicating no new datatransmission (e.g. adaptive retransmission).

A WTRU retransmission may perform, for example, one or more actions.

In an example (e.g. when a valid eRAR may not have been received or areceived eRAR may not have a matching WTRU ID), a WTRU retransmissionmay, for example: (i) repeat preamble selection and data transmission inthe first step of the 2-step process; (ii) repeat the first step of the2-step process utilizing the same preamble, preamble resources and/ordata resources; (iii) increase transmission power on preamble and/ordata transmission; (iv) initiate a 4-step procedure (i.e. transmit onlypreamble); and/or (v) repeat preamble selection and data transmission inthe first step of the 2-step preamble, with or without employing adifferent set of or subset of preambles or a different selectioncriteria for preamble/data resources. For example, a WTRU may selectfrom a more robust set of preambles following a failed preamble+datatransmission. A more robust set of preambles may correspond totransmission of data in a different numerology block, differentfrequency range, using different WTRU encoding, etc.

In an example (e.g. when a valid eRAR may have been received with NACKon data or ACK and NDI=0), a WTRU retransmission may, for example: (i)perform retransmission of data only, e.g., using a TAC provided in aneRAR; (ii) perform retransmission of data, with or without anotherredundancy version associated with the data, which may be indicated inthe eRAR or based on a pre-defined sequence; (iii) modify the guardinterval configuration for retransmission of preamble+data; (iv) performretransmission of data only, e.g., re-utilizing the same data resourcesas the initial transmission, with or without retransmission of thepreamble; (iv) perform retransmission utilizing UL grant, which may beprovided in the eRAR; (v) modify the MCS used for data transmission touse the MCS provided by the grant; (vi) scale the MCS by a specificamount (e.g. a scaled MCS may be determined based on the ability toretransmit data on a resource without the need for a guard interval)and/or (vii) reset its TA timer and assume it is currently timingaligned.

In an example, a WTRU may perform retransmission of preamble+data (e.g.repeat 2-step process) under one or more of the following occurrences:(i) the WTRU may not receive an eRAR within the expected time period;(ii) the WTRU may receive an eRAR with a WTRU ID that may not match theWTRU's own ID or the ID transmitted by the WTRU during the 2-stepprocess and/or (iii) the WTRU may receive an eRAR that may be intendedfor it with a HARQ process state corresponding to NACK (non-adaptiveretransmission).

A WTRU may (e.g. further) modify a guard interval configuration forretransmission of preamble+data, for example, as a result of requiring aretransmission, e.g., where the WTRU may have received a valid TAC inthe eRAR. In an example, a WTRU may perform retransmission ofpreamble+data without a guard period, for example, when the WTRU mayreceive an eRAR that may be intended for it, e.g., where NACK and avalid TAC may be received without a UL grant.

In an (e.g. another) example, a WTRU may receive a valid eRAR that maycontain NACK (or ACK with NDI=0) and a UL grant, e.g., including MCS,resources, etc. The WTRU may retransmit the data part (which may havebeen initially transmitted in the preamble+data), for example, using theprovided grant. A UL transmission may (e.g. also) be performed by theWTRU, for example, using UL timing provided in an eRAR.

In an (e.g. another) example, a WTRU may receive a valid eRAR that maycontain a NACK without UL grant information in the eRAR. The WTRU mayretransmit the data (e.g. without a preamble), for example, using thesame resources selected for the data part in the initial transmission.Resources may be located in a subframe/frame whose timing may depend onreception timing of an eRAR. A WTRU may (e.g. further) determine thatresources may be dedicated for its own transmission (e.g.non-contention-based). A WTRU may (e.g. further) transmit in suchresources without the use of guard interval and may compensate for thelack of guard interval, for example, by performing one or more of thefollowing: (i) increasing coding (e.g. changing MCS) so the ULtransmission may occupy an entire time duration of the resource; (ii)transmitting an additional (e.g. new TB) with the original (e.g.retransmitted) TB using the same resource and/or (iii) transmitting in asubset of the resources (e.g. where the subset may be indicated by theeRAR). For example, a WTRU may transmit over a first slot of amulti-slot resource or may transmit over a known subset of resourceblocks associated with the initial resource.

An enhanced Message 2 (eMSG2/eRAR) may be provided. A WTRU may (e.g.following a transmission that may include a preamble) receive anenhanced random access response (eRAR) from a network.

An eMSG2 reception procedure may include an eRAR reception procedure. AWTRU may perform decoding for an eRAR, e.g., following transmission ofeMSG1. A WTRU may determine successful reception of an eRAR, forexample, when an eRAR may be successfully decoded at an expected ordefined time and/or within a specific time interval. A WTRU may initiatea failure procedure, such as retransmission procedure, for example, whenan eRAR may not be successfully decoded at a specified time or during aspecified eRAR reception window.

In an example, an eRAR may be received by a WTRU at a specific time(e.g. subframe, slot, mini-slot).

A WTRU may determine eRAR reception time based on one or more (e.g. acombination) of the following, for example.

A WTRU may determine eRAR reception time, for example, based on a timefrom transmission of preamble/data. A WTRU may determine eRAR receptiontime based on (e.g. number of subframes following) the transmission ofthe preamble and/or data. A time may be preconfigured in the WTRU orconfigured by a network.

A WTRU may determine eRAR reception time, for example, based on aselected preamble. An eRAR reception time may depend on a selectedpreamble sequence, which may relate to the type of transmissionperformed by the WTRU. For example, a WTRU may determine an eRARreception time to be a specific time following transmission of apreamble, where that time may be different depending on the selectedpreamble. A WTRU may expect a shorter time delay until reception of theeRAR, for example, for low-latency data transmission, which may beindicated by a selected preamble.

A WTRU may determine eRAR reception time, for example, based onresources selected by the WTRU. A WTRU may determine an eRAR receptiontime as a function of the resources selected for transmission of apreamble and/or data.

A WTRU may determine eRAR reception time, for example, based onreception of a synchronization symbol. A WTRU may determine an eRARreception time based on the timing of one or more synchronizationsymbols that may be received from a network. For example, a WTRU maycompute an RAR reception time as a time window starting from receptionof a synchronization symbol that may be measured by the WTRU, e.g., withthe best or suitable measurements.

A WTRU may determine eRAR reception time, for example, based on a WTRUID. A WTRU may determine an eRAR reception time as a function of a WTRUID, e.g., transmitted as part of an initial preamble+data transmission.

A WTRU may determine eRAR reception time, for example, based on a typeof data/service transmitted by a WTRU. A reception time of an eRAR maybe specific to or may depend on the type of data/service that may betransmitted by the WTRU, which may be identified by the WTRU in a datatransmission, e.g., based specific control information, transmissionproperties of the data or selection of preamble sequence, resources,etc.

These examples alone or in any combination may permit a network todistribute the load for eRAR transmission, such as in situations wheremultiple WTRUs may have an eRACH procedure triggered simultaneously.These examples alone or in any combination may allow prioritization ofeRAR, e.g., for low-latency transmissions over eRAR fornon-time-critical transmissions. A WTRU may move to power-saving stateduring a period between preamble+data transmission and eRAR reception,for example, when it is aware of a longer time period between the two.

In an example, an eRAR reception time may be specific to or may dependon the type of data/service being transmitted by WTRU. A WTRU may expectan eRAR to be sent at a fixed time instant or during a configurablewindow of time following eMSG1 transmission. A time may be determined,for example, by the type of data that may be transmitted by the WTRU inthe first step (preamble+data transmission). The data type may beindicated by the WTRU, for example, using a MAC CE, which may betransmitted with the data (e.g. by indication of a data type, logicalchannel, or similar field).

A WTRU may expect eRAR to be repeated in multiple resources (e.g. intime, frequency, space or code). This may enable a WTRU to use Chasecombining or incremental redundancy of the eRAR, e.g., for improvedreliability and error avoidance (e.g. when a WTRU erroneously assumes noeRAR was transmitted). This may (e.g. for URLLC scenarios) avoidmultiple unnecessary RACH procedures. An eRAR may provide a UL grant orDL assignment for a subsequent transmission. An eRAR may beretransmitted multiple times in the time domain. A UL grant or DLassignment portion of an eRAR may change for each repetition. This mayenable a WTRU (e.g. that may correctly detect and decode eRAR before allretransmissions are completed) to perform UL or DL transmission morequickly.

A WTRU may expect an eRAR based on a reception window (or period oftime). The starting time for a window may be determined, for example,based on one or more previously described determinations for receptionof eRAR at a specific time and/or based on one or more otherdeterminations.

A reception window length may be determined, for example, based onconfiguration. A reception window may be determined, for example, basedon network configuration or may be preconfigured at the WTRU.

A reception window length may be determined, for example, based onnetwork load (e.g. measured or signaled). A WTRU may determine a lengthof an eRAR reception window, for example, based on a current networkload. For example, a WTRU may determine a network load from anindication from the network. A WTRU may (e.g. also) determine a networkload based on measurements of a medium (e.g. energy detection, sensing),which may be combined with measurements used to access the medium foreMSG1 transmission. A procedure may be applicable for operation inunlicensed spectrum, for example. A WTRU may (e.g. further) determinereception window length as a (e.g. predefined or configured) function ofa network load.

A reception window length may be determined, for example, based on asynchronization sequence. A WTRU may determine the length of a receptionwindow, for example, based on a synchronization sequence detected by theWTRU. For example, a determination may be made by a WTRU based on theidentity of synchronization sequence. A synchronization sequence maycorrespond to a sequence with the largest received power at a WTRU. Theidentity of a sequence may be encoded, for example, using sequencepattern, timing and/or other physical properties associated with thesequence. A WTRU may determine reception window length, for example,using a lookup table of reception window length associated withsynchronization sequence identity. A lookup table may be preconfiguredin a WTRU, configured by network signaling or may be part of an accesstable obtained by the WTRU from a network.

A reception window length may be determined, for example, based on beamproperties of synchronization sequence reception or eMSG1 transmission.A WTRU may determine a reception window as a function of beam propertiesat a WTRU used for detecting a synchronization sequence. For example, aWTRU may perform beamforming/beamsweeping to detect a synchronizationsequence. A WTRU may determine an eRAR reception window length, forexample, as a (e.g. preconfigured or network configured) function of thebeam angle at the WTRU for synchronization reception. A WTRU may (e.g.alternatively) compute reception window length as a function of beamsweeping parameters of an eMSG1 transmission.

An eRAR may be received by a WTRU by decoding one or more controlchannels defined for a cell/TRP and/or associated with a synchronizationsequence. A WTRU may receive an eRAR, for example, through a downlinkassignment addressed through DCI to the WTRU or to a group of WTRUs.

A WTRU may decode a control channel, for example, using an RNTI that maybe specific to a cell/TRP/synchronization sequence. An RNTI for decodingeRAR may be determined by a WTRU based on one or more of the following.

An RNTI for decoding eRAR may be determined based on, for example, anRNTI preconfigured in the WTRU.

An RNTI for decoding eRAR may be determined based on, for example, anRNTI received from system information. For example, a WTRU may determinean RNTI to decode for reception of eRAR from system information providedby the cell/TRP.

An RNTI for decoding eRAR may be determined based on, for example, anRNTI associated with synchronization sequence. A WTRU may determine RNTIfrom a synchronization sequence or identity encoded in a synchronizationsequence. A WTRU may use an RNTI that may be the same as asynchronization sequence identity or a sub-portion of thesynchronization sequence identity. A WTRU may (e.g. alternatively)determine RNTI as a preconfigured function of a synchronizationsequence.

An RNTI for decoding eRAR may be determined based on, for example, anRNTI derived from preamble sequence. For example, a WTRU may use apreamble sequence (e.g. transmitted in eMSG1) or a portion thereof, asthe RNTI.

An RNTI for decoding eRAR may be determined based on, for example, anRNTI derived from selected preamble/data resources. A WTRU may determinean RNTI based on resources selected for a preamble and/or datatransmission, A mapping of resources (e.g. frequency location, resourceblock index, subframe number or similar) may be provided to a WTRU orpreconfigured in a WTRU. A WTRU may derive its RNTI from such a mappingand the selected preamble/data resources for eMSG1.

An RNTI for decoding eRAR may be determined based on, for example, anRNTI based on WTRU ID. For example, a WTRU may use, e.g. as RNTI, anidentity transmitted by the WTRU during eMSG1 or provided to the WTRU(e.g. through network order or eMSG0).

In an example, a WTRU may determine RNTI as a function of a preamblesequence and selected resources for transmission of a preamble. A firstset of bits of the RNTI may correspond to a certain number of bits ofthe preamble. A second set of bits of the RNTI may be associated withselected resources. In an example, resources for a transmission of thepreamble may be identified, for example, using sequential numbering,e.g., in terms of increasing frequency and/or time (e.g. for a specificsubframe, frame, frequency band, etc.) and may be used by the WTRU todetermine the second set of bits. A third set of bits in the RNTI may bea preconfigured sequence.

A WTRU may receive eRAR reception while decoding one or more controlchannels. A WTRU may determine a specific control channel (e.g. whenthere may be multiple control channels) or specific resources of acontrol channel (e.g. CCE, subband, frequency block or similar) on whichan eRAR may be received. A subset of resources may be determined by theWTRU, for example, based on one or more of the following.

A subset of resources may be determined, for example, based on apreamble sequence and/or resources selected by a WTRU. For example, aWTRU may select control channel resources to perform decoding for eRARbased on a function of a selected preamble, the resources used totransmit the preamble and/or additional service-related information thatmay be sent during transmission of the preamble and data. For example, aWTRU may select control channel resources associated with a referencenumerology block or for a numerology block associated with a type ofservice requested during transmission of preamble+data.

A subset of resources may be determined, for example, based on asynchronization sequence detected by a WTRU. A WTRU may select (e.g.based on a pre-defined or configured rule) control channel resourcesthat may be associated with the best synchronization sequence detectedby the WTRU, e.g., prior to or during performance of the first step ofthe 2-step procedure. For example, a WTRU may determine a time/frequencylocation of control channel resources based on a relationship betweensynchronization sequence timing/frequency and its corresponding controlchannel resources.

A subset of resources may be determined, for example, based on a currentconnection: A WTRU may (e.g. alternatively) receive eRAR on specificcontrol channel resources that may be defined for eRAR reception for aspecific cell/TRP/set of beams the WTRU may be currently connected towhen it performs transmission of data+preamble.

Reducing the expected frequency range (decoding range) for eRARreception may provide significant power savings for WTRUs that may betransmitting only occasionally and may use the 2-step procedurecontinually to perform their transmission. For example, randomization ofresources on which eRAR may be sent (e.g. by having it depend on theselected preamble, which may be selected partially randomly) may resultin significant power savings for a WTRU without reduction in networkscheduling flexibility for eRAR.

eRAR may be received with specific beam parameters. A WTRU may receiveeRAR on any downlink beam transmitted by the network.

A WTRU may (e.g. alternatively) receive eRAR using beam parameters thatmay be a function of its eMSG1 transmission. A WTRU may determine itsbeam parameters based on one or more of the following:

A WTRU may determine its beam parameters, for example, based onpreamble, preamble resources and/or data resources selected/used by theWTRU during transmission of eMSG1.

A WTRU may determine its beam parameters, for example, based ontransmission parameters of data transmitted in eMSG1 (e.g. MCS, TB size,estimated transmit power).

A WTRU may determine its beam parameters, for example, based onbeamforming parameters applied for the preamble or data transmissionused for eMSG1. A WTRU may receive eRAR, for example, in a downlink beamat an angle of arrival (AoA) close to or overlapping with the angle ofdeparture (AoD) of the uplink eMSG1 transmission where the may beexpected.

A WTRU may determine its beam parameters, for example, based onproperties or parameters of a downlink beam in which a WTRU may receivea configuration related to an eMSG1 transmission where the eRAR may beexpected. In an example, a WTRU may monitor eRAR, for example, using anidentity based on a downlink beam index, eMSG1 transmission slot orsub-frame number and/or frequency allocation index. This may (e.g.further) reduce contention of the procedure, for example, when onlyWTRUs that received eMSG transmission configuration within the same beam(e.g. not the same cell) may monitor the eRAR.

An eRAR may include one or more types of information.

An eRAR may include, for example, an identifier (or equivalent). An eRARmay contain an identifier that may provide an indication of the identityof WTRUs that may be detected to have transmitted eMSG1. This mayconsist of an echo of the preamble or a portion of the preamble orindication whether contention was detected for a specific preamble.

An eRAR may include, for example, HARQ Feedback. An eRAR may containHARQ feedback for data (e.g. ACK/NACK). Feedback may be explicit, suchas a bit or field in a MAC CE that may be included in the eRAR. HARQfeedback may be implicitly indicated by, for example, the presence ofother fields or information. For example, the presence of a UL grant mayimplicitly specify a NACK.

An eRAR may include, for example, uplink timing information (e.g. aTiming Advance Command (TAC) or an indication whether the WTRU is timingaligned).

An eRAR may include, for example, one or more downlink assignment(s). AneRAR may contain (e.g. as a MAC CE) one or more downlink assignments forDL data destined for the WTRU, e.g., including MCS, HARQ process number,resources, timing, etc.

An eRAR may include, for example, information enabling reception of adownlink assignment. An eRAR may contain information enabling subsequentor further reception (e.g. by a WTRU) of downlink assignments, such asan RNTI, specific time/frequency location of a DCI, specific controlchannel on which the WTRU may perform additional decoding for DLassignments, etc.

An eRAR may include, for example, one or more uplink grant(s). An eRARmay contain one or more UL grants, e.g., including MCS, resources, HARQprocess number, redundancy version, power control, etc. An eRAR may(e.g. also) indicate whether a UL grant may be used for retransmissionof data in eMSG1 (e.g. including RV) or whether the grant may be usedfor transmission of new data. An indication may be supported, forexample, using an NDI, and may serve as implicit indication of ACK/NACK(e.g. NDI=1 may signal ACK and grant assumed for new data transmission).An indication whether retransmission may be needed may be provided basedon TB size (e.g. when the TB size for the grant matches the initial datasize, is a predefined size used to signal retransmission or is apredefined function of the initial data TB size that specificallysignals retransmission).

An eRAR may include, for example, contention-resolution information. AneRAR may contain an indication whether a contention (e.g. duringtransmission of eMSG1) was detected and may indicate information to beused by the WTRUs in question to resolve the contention. This mayconsist of information contained in a WTRU's transmission, such as aWTRU ID that may have been transmitted by the WTRU in eMSG1. Informationmay (e.g. also) consist of an echo of a portion of the data transmittedby the WTRU, e.g. when successfully decoded. Information may (e.g. also)consist of an indication of a detected transmit power/path loss/antennaparameters/beamforming parameters that may be associated with a WTRU'stransmission (e.g. determined from decoding eMSG1 from the WTRU).

An eRAR may include, for example, backoff information. An eRAR maycontain a backoff time or backoff instructions (e.g. perform 4-stepPRACH procedure instead). A WTRU may delay retransmission of eMSG1,retransmission of data, or may be redirected to using PRACH as a resultof receiving such information.

An eRAR may include, for example, an indication whether to initiate anRRC CONNECTION procedure. An eRAR may contain an indication to a WTRUwhether it should initiate an RRC CONNECTION procedure, for example, bytransmission of an RRC ConnectionRequest message. A WTRU may transmit amessage, for example, using a provided UL grant in the eRAR. Anindication whether to remain in the inactive state or transition to RRCCONNECTED may (e.g. alternatively) be determined implicitly through theuse of other information. For example, a WTRU may determine that it mayremain in an inactive state in the absence of a UL grant in the eRARcombined with an ACK. A WTRU may initiate an RRC Connection, forexample, in the presence of a UL grant and ACK.

Contention resolution may be provided, e.g., following eRAR reception. AWTRU may receive eRAR on a control channel (e.g. PDCCH or similar) bydecoding the message using a WTRU identifier. In an example, a WTRU mayuse an ID to decode PDCCH, which may correspond to an ID sent, at leastin part, by the WTRU during transmission of preamble+data in the firststep. A WTRU may compute the ID for decoding of PDCCH using one or moreof: (i) all or part of the preamble sequence; (ii) a function of theresources selected for transmission of the preamble and/or the data;(iii) all or part of an explicit WTRU identifier transmitted as part ofthe data during preamble+data transmission (e.g. in a MAC CE includedwith data transmission); (iv) a permanent ID configured in the WTRUand/or (v) an identifier that may correspond to a signature sequence orreference sequence detected/measured by the WTRU prior to transmissionof preamble+data.

In an (e.g. alternative or additional) example, which may be used incombination with other examples, a WTRU may determine that it is theintended recipient of the eRAR, for example, by determining whether anID present in the payload of the eRAR contains a part or all of thetransmitted ID. Decoding of PDCCH may be made on a generic ID (e.g.RA-RNTI) or based on one or more elements described herein (e.g.preamble sequence, preamble/data resources selected).

In an example, a WTRU may (e.g. first) perform decoding of an eRARmessage, e.g., using a first ID (ID1) and may search for a second ID inthe eRAR payload (ID2). A WTRU may take action on the eRAR (e.g. updateits HARQ buffers based on the received HARQ process state), for example,when the combination of ID1 and ID2 matches the ID transmitted by theWTRU in the preamble+data transmission.

In an (e.g. another) example, a WTRU may decode PDCCH, for example,using an ID that may be derived from, or directly related to, theselected preamble sequence and/or preamble resources. A WTRU may (e.g.then) determine whether the eRAR is intended for it, for example, bydetermining whether the ID included in the payload matches (e.g. inwhole or in part) a permanent ID configured at the WTRU.

HARQ feedback may be provided. A WTRU may receive, in the eRAR orthrough other signaling (e.g. related to the eRACH procedure), HARQfeedback from the network for the data transmitted in eMSG1. Feedbackmay consist of, for example HARQ ACK/NACK, a HARQ process numberidentifying the HARQ process being acknowledged and/or a redundancyversion indicating the code-block required for retransmission.

HARQ feedback may be explicit. A WTRU may receive HARQ feedback (e.g. abit whose value indicates ACK or NACK, or a value of HARQ processnumber), for example, in the eRAR or signaling associated with receptionby the WTRU of the eRAR.

HARQ feedback may be indicated, for example, as a flag or field in a MACCE transmitted in the eRAR. A WTRU may receive (e.g. as part of or aseRAR itself) a MAC CE that may contain one or more explicit fields forHARQ feedback. For example, a WTRU may receive an ACK/NACK bit and/or anNDI. In an example, a WTRU may receive ACK, for example, when theACK/NACK field may be set to 1 and/or the NDI field may be set to 1. Inan example, a WTRU may receive NACK, for example, when the ACK/HACKfield is not present and the NDI is set to 0. Other combinations offields are contemplated.

HARQ feedback may be indicated, for example, in DCI on (e)PDCCH. A WTRUmay receive HARQ feedback in the DCI used to signal DL allocation forthe eRAR. For example, a WTRU may receive HARQ feedback with specificfields in the DCI. Alternatively, or in conjunction, all or part of theHARQ feedback may be indicated based on the specific (set of) CCE(s),search space, RNTI, or the like in which the DCI may be decoded by theWTRU. For example, a WTRU may receive a HARQ process number based onCCEs used to decode the DCI or a specific search space in which eRAR wasreceived.

HARQ feedback may be indicated, for example, in higher layer messaging.A WTRU may receive (e.g. as part of or as the eRAR itself) a transportblock containing control signaling (e.g. RRC), which may contain a (e.g.explicit) message or indication of HARQ ACK/NACK (e.g. an RRC message).

Explicit HARQ feedback may be associated with other signaling. In anexample, a WTRU may receive explicit HARQ feedback on signaling otherthan the eRAR.

A WTRU may receive explicit HARQ feedback, for example, using a separatededicated control channel. A WTRU may receive HARQ feedback from acontrol channel or control channel resources dedicated for transmissionof HARQ feedback, which may be associated with eRACH HARQ feedback. Thetime/frequency location of a dedicated resource may be indicated to aWTRU, for example, through broadcast or dedicated signaling. In anexample, a PHICH-like resource element for transmitting ACK/NACK mayprovide an indication, where the specific resource used may furthersignal the HARQ process number.

A WTRU may determine a time/frequency location of HARQ feedbackresources, for example, based on properties of a eRACH procedure. Forexample, a WTRU may determine the time/frequency location of controlresources for HARQ feedback as a function of: (i) a selected preamble,selected preamble resources and/or selected data resources; (ii) aWTRU's identity, such as its C-RNTI, RA-RNTI or similar and/or (iii) thetiming of a transmitted preamble and/or data resources.

A WTRU may receive explicit HARQ feedback, for example, using a separateDCI message. A WTRU may receive ACK/NACK, for example, using a separateDCI message (e.g. other than the one received for eRAR). The timing of aDCI message may be related to the timing of reception of an eRARmessage. For example, a WTRU may receive a DC message containingACK/NACK on the same or subsequent subframe, slot or mini-slot.

Implicit HARQ feedback may be provided, for example, by presence/lack ofmessaging associated with eRAR. In an example, a WTRU may receive HARQfeedback implicitly based on the presence/absence of eRAR ormessage/field associated with the eRAR.

In an example, a WTRU may assume ACK, for example, when it receives eRAR(e.g. based on decoding with the associated C-RNTI or RA-RNTI, asapplicable).

In an (e.g. another) example, a WTRU may assume ACK, for example, whenit receives eRAR, which may contain an identity that may match the WTRUID transmitted in eMSG1. A WTRU may assume NACK, for example, when itdoes not receive eRAR or when it receives eRAR with an identity in theeRAR that may not match the WTRU ID transmitted in eMSG1.

In an (e.g. another) example, a WTRU may assume NACK, for example, whenit receives a grant in the eRAR that may be associated with (i) a HARQprocess number of the data transmission in eMSG1, which may be pending(e.g. assuming single parallel eMSG1 data transmissions), or (ii) a HARQprocess number associated with the data transmission in an eMSG1 thatmay have occurred in a specific number of subframes, slots, mini-slots,e.g., prior to the reception of the eRAR.

Upon determination of a HARQ ACK, the WTRU may perform the procedureassociated with successful completion of the eRACH procedure asdescribed herein. A WTRU may further perform uplink transmission on theassociated grant received (if such grant is included in the eRAR) basedon the rules associated with that grant. Specifically, the WTRU mayperform transmission based on the MCS and HARQ process ID associatedwith the grant.

A WTRU may (e.g. for HARQ NACK) perform one or more procedures, forexample, in all cases (e.g. upon initial reception of NACK) or dependingon one or more conditions, such as example conditions indicated herein.

A WTRU may perform retransmission of eMSG1, for example, when one ormore of the following conditions exists: (i) the WTRU determines a HARQNACK and eMSG1 contain no grant; (ii) the WTRU determines a HARQ NACKfollowing its maximum number of HARQ retransmissions for data in eMSG1(which may be configured or fixed for a specific WTRU); (iii) the WTRUdetermines a HARQ NACK and frequency of operation, preamble sequenceutilized, synchronization sequence, or other indication that the NACKmay require retransmission of eMSG1 and/or (iv) the above occurs aridthe number of retransmissions may be less than a maximum number ofretransmissions for eMSG1 (which may be configured or fixed for aspecific WTRU).

A WTRU may perform adaptive HARQ retransmission of the data portion ofeMSG1, for example, when one or more of the following conditions exists:(i) the WTRU determines a HARQ NACK in combination with a UL grant foreMSG1 with or without a HARQ process ID in the grant that may match aHARQ process ID of an initial transmission and/or (ii) the above occursand the number of retransmissions may be less than a maximum number ofretransmissions for eMSG1 (which may be configured or fixed for aspecific WTRU).

A WTRU may perform failure of the eRACH procedure, for example, when oneor more of the following conditions exists: (i) the WTRU determines aHARQ NACK and the number of retransmissions has reached the maximumnumber of retransmissions for the data in eMSG1 and/or (ii) the WTRUdetermines a HARQ NACK and the number of retransmissions has reached themaximum number of retransmissions for the data in eMSG1.

WTRU behavior may be based on a combination of information received fromthe ACK/NACK, UL Grant and a backoff indication.

A WTRU may perform HARQ retransmission or retry eRACH procedure (e.g. asdescribed herein), for example, when a backoff indication is notprovided.

A WTRU may receive an indication to perform backoff and an ACK may bereceived. A WTRU may perform subsequent data transmission based on a4-step procedure and may move to connected state (e.g. when configuredto do so). A WTRU may perform subsequent data transmissions based on2-step procedure, for example, (e.g. only) when the next transmissionoccurs, e.g., after a configured or predefined time.

A WTRU may receive an indication to perform backoff and an NACK may bereceived. A WTRU may initiate an RRC connection, for example, when theWTRU is provided with a UL grant. The WTRU may use the UL grant totransmit an RRC Connection Request message. A WTRU may retransmit data,for example, by reusing the eRACH procedure, e.g., after waiting aconfigured or predefined time period. A WTRU may initiate a 4-stepprocedure (e.g. immediately), for example, when the QoS may require datato be transmitted with minimal latency.

Contention resolution may be provided. A WTRU may determine whethercontention or collision occurred during transmission of eMSG1, e.g.,through one or more procedures described herein. A WTRU may (e.g. inresponse to contention) initiate a contention resolution procedure,which may consist of a (contention-based or contention-free) datatransmission, a retransmission of eMSG1 (potentially with differentpreamble resource/sequence selection) and/or a retransmission of thedata part of eMSG1.

A WTRU may detect contention and may determine that it needs to initiatecontention resolution as a result of one or more of the following:

A WTRU may initiate contention resolution, for example, based on HARQA/N in eRAR for initial transmission. For example, a WTRU may determinefrom reception of a NACK, with or without additional information in theeRAR (e.g. a UL grant) that the WTRU may need to perform contentionresolution.

A WTRU may initiate contention resolution, for example, based onreception of an eRAR with a specific RNTI. For example, a WTRU maydetermine the presence of contention based on the reception of an eRARor similar message using an RNTI other than the RNTI for successful(e.g. no contention) case. In an example, a WTRU may determine thepresence of contention, for example, when it receives a message usingRA-RNTI instead of using C-RNTI.

A WTRU may initiate contention resolution, for example, based onreception of an eRAR with a specific RNTI. For example, a WTRU maydetermine the presence of contention based on the reception ofadditional grants (e.g. more than 1) in the eRAR.

In an example, a WTRU may perform contention resolution through a ULtransmission indicating contention resolution. An uplink transmissionmay contain an identity of the WTRU. An uplink transmission may containthe data (e.g., retransmitted, potentially with a different redundancyversion) in eMSG1. A transmission may occur, for example, based on atransmission using a grant in eRAR.

A WTRU may perform transmission associated with contention resolution,for example, by sending the contention resolution information (e.g. ID,retransmitted data, etc.) in the UL grant provided in the eRAR.

A WTRU may maintain a HARQ process state received in the eRAR during thecontention resolution procedure. A WTRU may assume the HARQ processstate received in the eRAR, for example, upon successful contentionresolution (e.g. the WTRU may determine that eRAR was intended for it).A WTRU may delete/ignore the information in the eRAR, for example, forfailed contention resolution.

A WTRU may perform (e.g. adaptive HARQ) retransmission for a dataportion of eMSG1, for example, when the WTRU receives one or more ULgrants in eMSG1.

A WTRU (e.g. upon reception of the eRAR) may perform retransmission ofthe data in eMSG1, e.g., using the MCS provided in the UL grant.

A WTRU may receive multiple UL grants in eRAR. A WTRU may select a ULgrant used for adaptive retransmission of the data part of eMSG1, forexample, based on one or more of the following: (i) selection of aspecific grant (e.g. a WTRU may select a first grant in the eRAR); (ii)random selection of a grant (e.g. a WTRU may randomly select among thegrants provided in the eRAR); (iii) indication of the HARQ process ID(e.g. a WTRU may select a UL grant containing a HARQ process ID matchinga HARQ process ID of data in eMSG1 sent by the WTRU); (iv) comparison ofgrant size with data to be transmitted (e.g. a WTRU may select the grantthat best suits data to be transmitted based on the MCS in the grant oraccommodates retransmission of the data and minimizes the amount ofpadding to be transmitted) and/or (v) priority of the data (e.g. a WTRUmay select a grant based on the priority of the data and the associatedproperties of the grant, such as numerology, ref ability, etc.). In anexample, a WTRU may select a grant with shorter TTI, for example, whenthe data to be retransmitted may have strict timing requirements. Anassociation may be based on a logical channel or highest prioritylogical channel of the data in the transport block to be retransmitted.

A WTRU may perform one or more procedures for failure of an eRARprocedure, for example, based on one or more of the following: (i)failure to receive eRAR following a maximum number of eMSG1retransmissions and/or (ii) one or more failure conditions associatedwith NACK.

A WTRU may (e.g. upon failure of an eRAR procedure) perform one or moreof the following: (i) declare Radio Link Failure (RLF); (ii) performcell reselection; (iii) revert to normal RACH procedure (e.g. WTRU maytransmit preamble according to rules associated with RACH (4-step)procedure); (iv) transmit data on contention-based resources and/or (v)perform backoff for a fixed or configured period of time before retryingthe eRAR procedure.

An eRACH completion procedure may be provided, e.g., upon successfultransmission. A WTRU may determine its data transmission during apreamble+data transmission was successful (e.g. successfully decoded bythe network), for example, upon reception of an eRAR with HARQ A/N setto ACK. A WTRU may (upon successful transmission) perform one or more ofthe following actions.

A WTRU (e.g. upon successful transmission) may, for example, reset itsTA timer and assume it is currently timing aligned for future ULtransmissions.

A WTRU (e.g. upon successful transmission) may, for example, determinewhether a UL grant was provided in the eRAR.

A WTRU may, for example, when a UL grant is provided in the eRAR,perform one or more of the following: (i) use the UL grant to performtransmission of any additional pending data for UL transmissions; (ii)use the UL grant to perform transmission of control information (e.g.buffer status or additional scheduling requests) and/or (iii) use the ULgrant to perform transmission of information related to state transition(e.g. RRC Connection Request).

A WTRU may, for example, when a UL grant is not provided in the eRAR andthe WTRU still has data to transmit in its buffers, perform one or moreof the following: (i) send a scheduling request or buffer statusinformation assuming UL timing alignment and/or (ii) perform a 2-stepprocedure with a different guard period configuration (e.g. no guardperiod).

A WTRU may, for example, when a UL grant is not provided in the eRAR andthe WTRU does not have data to transmit, perform one or more of thefollowing: (i) perform DRX and/or (ii) perform a state transition, suchas to IDLE or light connected state.

Systems, methods, and instrumentalities (e.g. in a wirelesstransmit/receive unit (WTRU) and/or network layers L1, L2, L3) have beendisclosed for random access in next generation wireless systems. Atwo-step random access procedure may permit a WTRU to select a preamblesequence (e.g. based on its desired data transmission). A WTRU mayselect data transmission resources, MCS and numerology associated withthe preamble. A WTRU may transmit a preamble in the preamble resourcesand data in the data resources (e.g. resources may be joint ordisjointed). A WTRU may receive an enhanced random access response(eRAR), which may include HARQ feedback. Procedures may be provided foran enhanced message 0 (eMSG0), e.g., network order, and relatedprocedures, selection of an enhanced random access channel (eRACH)versus RACH, eMSG1 (e.g. preamble+data transmission) and relatedprocedures, eRAR and related procedures, hybrid automatic repeat request(HARQ) and retransmission related procedures for the data part of atransmission and contention-based resolution procedures. A network mayprovide a WTRU with a (e.g. per) bearer configuration for an eRACHprocedure (e.g. while in an inactive state). New/dedicated bearers maybe provided for WTRU transmission (e.g. while in an inactive state).

A scheduling request (SR) procedure may be performed using RACH, eRACHor dedicated SR. A WTRU may perform an SR procedure using a randomaccess procedure, using the eRACH procedure, e.g. by including a BSRand/or data in the MSG1 transmission, or using a dedicated resource e.g.D-SR.

The WTRU may initiate a scheduling request. Such a scheduling requestmay be performed using a dedicated resource, e.g. if configured for theWTRU. For example, a D-SR may be sent using a transmission on a PUCCHresource or similar. Such scheduling request may be performed using ashared, possibly contentious, resource such as a RA-SR via a randomaccess procedure using a transmission on PRACH or similar. Suchscheduling request may be performed using a shared, possiblycontentious, resource such as an eRA-SR using an enhanced random accessprocedure using a transmission on PRACH or similar, as described herein.For example, an MSG1 may be included the concerned data, e.g. the datathat triggered the use and/or request of transmission resources.

For example, the WTRU may initiate a scheduling request when new databecomes available for transmission. Such data may be associated with oneor more QoS parameters such as a maximum delay budget, a discard timer,a maximum time until successful transmission and/or the like. Forexample, data associated to an ultra-low latency service (or the like),to a discard function and/or to a specific radio bearer may no longer beuseful or relevant for transmission after a certain amount of time. Theamount of time may be preconfigured or dynamically configured. Such timemay correspond to the time elapsed from the moment the WTRU determinesthat the data is available for transmission.

The WTRU may initiate a scheduling request for data available fortransmission. The WTRU may determine that the maximum time requirementhas elapsed or may determine that the maximum time requirement willelapse before the next occurrence of a resource available for performinga scheduling request. The WTRU may perform such a determination for asubset of scheduling request procedure types (e.g. D-SR if configured,and/or RA-SR otherwise) or at types of scheduling request procedures.The WTRU may perform such determination considering one or moreadditional access methods including, but not limited to, transmission ofdata using a grant free resource, a contentious resource and/or using alisten-before-talk (LBT) access in an unlicensed spectrum or the like,if such is configured and/or available for the concerned data. The WTRUmay abort an ongoing scheduling request (or another type of access)and/or discard the concerned data. The WTRU may indicate to RLC that thecorresponding RLC PDU is not to be retransmitted by the RLC, e.g., ifsuch retransmission may be otherwise applicable (e.g. for a bearerconfigured with RLC AM).

The WTRU may interrupt the transmission of such data after it has beenincluded in a transport block and after a first HARQ transmission hasbeen performed for this transport block. For example, the transmissionmay be initiated using a MSG1 in the eRACH procedure. For example, thetransmission may be initiated using a resource granted by the network,e.g. a semi-persistently allocated resource, a dynamically assignedresource by DCI reception, and/or using a grantless transmissionprocedure such as a contention-based access for a PUSCH resource(CB-PUSCH). For example, the interruption of the transmission of suchdata may be network controlled. The WTRU may receive downlink controlsignaling for a HARQ process that indicates that a new transmission maybe performed for the associated HARQ process, e.g. a DCI that toggles aNDI for the corresponding HARQ process. The WTRU may autonomouslyinterrupt the transmission of such data, based on a determination thatthe WTRU may use a grant free resource or a contentious resource. Forexample, the WTRU may determine that the next occurrence of anunscheduled resource is after time has elapsed for the concerned data.For example, the WTRU may determine that an access to resources e.g.using an LBT access in an unlicensed spectrum or the like, exceeds themaximum time requirement for the concerned data. For example, the WTRUmay determine that an access to resources e.g. using an LBT access in anunlicensed spectrum or the like, is likely to exceed the maximum timerequirement for the concerned data. Upon such a determination, the WTRUmay abort an ongoing HARQ process and/or discard the concerned data. TheWTRU may indicate to RLC that the corresponding RLC PDU is not to beretransmitted by the RLC, e.g., if such retransmission may be otherwiseapplicable (e.g. for a bearer configured with RLC AM).

The WTRU may determine that data is no longer available fortransmission. For example, the concerned data may be consideredunavailable for transmission on a condition that the time elapsed sincethe WTRU first determined that the concerned data became available fortransmission exceeds a maximum amount of time. The WTRU may cancel thescheduling request (and/or the buffer status report). In an embodiment,the WTRU may cancel a scheduling request related to the concerned data.In an embodiment, the WTRU may cancel the scheduling request on acondition that the WTRU has not performed an initial transmission of aTB for the concerned data. Otherwise, the WTRU may suspend and/or abortthe HARQ process for the concerned TB.

The network may not have been aware of the data becoming available fortransmission. In some cases, the network may be unable to determine thatthe WTRU has discarded the concerned data. The network may be unable todetermine that the WTRU has cancelled a scheduling request and/or thatit has interrupted (or aborted) a transmission autonomously (e.g. in thecase where the WTRU attempted a transmission using unscheduled, possiblyshared, resources or in the case of LBT). The discarding of data may behidden to the network as a result of the latency of the access attemptof the WTRU. Such events may occur due to deteriorating radioconditions, sub-optimal link adaptation, radio link failure, congestion(e.g. for shared and/or contentious resources), failure to receive a RARfor RA-SR within a sufficiently short time, load in the cell or amismatch in the configuration of the WTRU for the concerned service.

The WTRU may notify the network of the data becoming unavailable fortransmission. The WTRU may determine that an uplink notification to thenetwork is to be initiated. The WTRU may perform at least one of thefollowing.

The WTRU may trigger the transmission of a MAC CE. The MAC CE mayindicate the discard of the data, the interruption of a schedulingrequest and/or the interruption of an ongoing HARQ transmission (e.g. incase of a grantless or LBT operation). The MAC CE may be an extendedversion of a BSR, e.g. that includes an indication of discarded data perLCH and/or LCG. The MAC CE may be included in the next transmission forthe concerned MAC instance. A new scheduling request may be triggered.

The WTRU may trigger the transmission of a status report, e.g. an RLCstatus report or the like. The report may indicate the discard of thedata at the transmitter such that the receiver may ignore the “missing”RLC PDU. The status report may be generated as a stand-alone PDU (e.g.RLC PDU) or piggybacked on the next available RLC PDU for the concernedpacket flow treatment (e.g. bearer). The PDU may be considered as newdata available for transmission may trigger a new scheduling request.

The WTRU may trigger the transmission of a status report e.g. a PDCP SR(or similar). The status report may indicate the discard of the data.The status report may be generated as a stand-alone PDU (e.g. PDCP PDU)or piggybacked on the next available PDU for the concerned packet flowtreatment (e.g. bearer). The PDU may be considered as new data availablefor transmission may trigger a new scheduling request.

The WTRU may initiate an L3/RRC reporting procedure. For example, theWTRU may initiate the transmission of a bearer-specific (or QoStreatment-specific) RRC radio link failure notification or the like. Thenotification may indicate the discard of the data, the concerned bearer,cause and/or QoS flow identity. The message may be generated as astand-alone PDU (e.g. RRC PDU). The PDU may be considered as new dataavailable for transmission may trigger a new scheduling request.

The uplink notification may be subject to a prohibit function. Forexample, a supervision function may be applied such that no more than x(e.g. x=1) of the above notification may be sent within a (e.g.configured) period of time. A notification prohibit timer may bestarted, e.g. when a notification is first available for transmission,The WTRU may refrain from generating any additional notification (e.g.,only for the same cause, if applicable) while the timer is running.

For example, the WTRU may subsequently receive a RRC connectionreconfiguration as a corrective action as a response from the network.

The WTRU may perform the following as a function of the type ofinterruption.

For dedicated SR (D-SR) interruption, the WTRU may determine that theWTRU may not use the associated set of resources, e.g. resourcescorresponding to a URLLC service if such resources have been used forthe interrupted D-SR procedure. The WTRU may determine to use a legacyRACH, e.g., using resources selected as a function of the type ofnotification. For example, the WTRU may use resources corresponding to adefault access and/or to a specific, e.g. longer, TTI duration.

For eRACH interruption with data-only or a BSR in MSG1, the WTRU maydelay using the eRACH procedure, e.g. until the WTRU determines that anuplink notification related to the concerned procedure has beensuccessfully received by the network (e.g. HARQ ACK is received for theconcerned transmission) and/or until the WTRU first receives an L3reconfiguration message. The WTRU may determine an access procedure touse e.g. a D-SR or legacy RACH, e.g., using resources selected as afunction of the type of notification. For example, the WTRU may useresources corresponding to a default access and/or to a specific, e.g.longer, TTI duration.

For random access interruption, the WTRU may determine not to use theassociated set of resources e.g. resources corresponding to a URLLCservice if such resources have been used for the interrupted RA-SRprocedure. The WTRU may determine to use a legacy RACH. For example, theWTRU may determine to use a legacy RACH only if resources different thanthose used for the interrupted RA-SR procedure are available.

FIG. 8 is an example flow chart of a WTRU determining whether to performan eRACH procedure or a legacy RACH procedure. A WTRU may initiate arandom access request. The WTRU may initiate the random access requestto perform a scheduling request and/or transmit an amount of data thatis below a predetermined threshold. At 802, the WTRU may determinewhether to select a first random access channel (RACH) procedure or asecond RACH procedure for the random access. The first RACH proceduremay be a legacy RACH procedure. The second RACH procedure may be anenhanced RACH (eRACH) procedure. At 802, the WTRU may determine whetherto select the first RACH procedure or the second RACH procedure based ona type of uplink data to be transmitted and/or the purpose of the randomaccess request. For example, as shown in FIG. 8, the WTRU may select thelegacy RACH procedure for type 2 data. Type 2 data may include enhancedmobile broadband (eMBB) data, for example. As another example, the WTRUmay select the eRACH procedure for type 1 data. Type 1 data may includeultra-reliable and low latency communications (URLLC) data, for example.

When the eRACH procedure is selected, the WTRU may perform one or moreof the following. At 804, the WTRU may select a set of preambleresources. The set of preamble resources may be associated with aneRACH. The WTRU may perform an eRACH procedure 806. The eRACH procedure806 may be a two-step RACH procedure. At 808, the WTRU may select apreamble resource from the set of preamble resources (e.g., selected at804). The preamble resource may be a physical random access channel(PRACH) resource, for example, associated with the eRACH procedure. Thepreamble resource may be an enhanced PRACH (ePRACH) resource. Thepreamble resource may include one or more of the preamble sequence, atime-frequency resource, and/or a numerology. The WTRU may determine apreamble sequence associated with the second RACH procedure. Thepreamble sequence may be determined based on one or more of the preambleresource, a data reception reliability, an amount of data to betransmitted, a maximum transport block size, a range of allowabletransport block sizes, a type of the RACH transmission, a triggerassociated with the RACH transmission, a timing requirement, a bufferstatus, a WTRU identity, a location, a numerology, a modulation andcoding scheme (MCS), a demodulation configuration, and/or multiplepreambles received from the network device.

At 810, the WTRU may determine a data resource for the uplink data basedon one or more of the preamble resource, the preamble sequence, the typeof uplink data, or a size of the uplink data. The data resource may bedetermined from a set of available resources. The set of availableresources may be indicated via one or more of system information, anaccess table, or a physical data control channel (PDCCH) grant to aspecific radio network identifier (RNTI).

At 812, the WTRU may send a RACH transmission to a network device usingthe at least one PRACH resource and/or the data resource. The RACHtransmission may include the preamble sequence and/or the uplink data.The preamble sequence and the uplink data may be disjoint in time and/orfrequency. The preamble sequence may be prepended to the uplink data.The WTRU may receive a random access response (RAR) message thatincludes an acknowledgment (ACK) or a negative acknowledgment (NACK)associated with the uplink data in the RACH transmission. The RARmessage may include an uplink grant. The WTRU may transmit additionalpending uplink data, control information, and/or state transitioninformation to the network device based on the uplink grant.

When the legacy RACH procedure is selected, the WTRU may perform one ormore of the following. At 814, the WTRU may select a set of preambleresources that may be associated with a legacy RACH. At 816, the WTRUmay perform a legacy RACH.

Example RRC configurations 818 for usable data resources may includepriority 1—short data, priority 2—short data, priority 1—long data, orpriority 2—long data. A first resource block (e.g., RB1) may be used forpriority 1, short data. A second resource block (e.g., RB2) may be usedfor priority 2, short data. A third and/or fourth resource block(s)(e.g., RB 5-6) may be used for priority 1, long data. A fifth and/orsixth resource block(s) (e.g., RB 7-8) may be used for priority 2, longdata.

The processes and instrumentalities described herein may apply in anycombination, may apply to other wireless technologies, and for otherservices.

A WTRU may refer to an identity of the physical device, or to the user'sidentity such as subscription related identities, e.g., MSISDN, SIP URI,etc. WTRU may refer to application-based identities, e.g., user namesthat may be used per application.

The processes described above may be implemented in a computer program,software, and/or firmware incorporated in a computer-readable medium forexecution by a computer and/or processor. Examples of computer-readablemedia include, but are not limited to, electronic signals (transmittedover wired and/or wireless connections) and/or computer-readable storagemedia. Examples of computer-readable storage media include, but are notlimited to, a read only memory (ROM), a random access memory (RAM), aregister, cache memory, semiconductor memory devices, magnetic mediasuch as, but not limited to, internal hard disks and removable disks,magneto-optical media, and/or optical media such as CD-ROM disks, and/ordigital versatile disks (DVDs). A processor in association with softwaremay be used to implement a radio frequency transceiver for use in aWTRU, terminal, base station, RNC, and/or any host computer.

What is claimed:
 1. A wireless transmit/receive unit (WTRU) comprising:a processor configured to: initiate a random access; determine whetherto select, for the random access, a first random access channel (RACH)procedure or a second RACH procedure based at least on a type of uplinkdata to be transmitted; when the second RACH procedure is selected, theprocessor being further configured to: determine at least one physicalrandom access channel (PRACH) resource associated with the second RACHprocedure; determine a preamble sequence associated with the second RACHprocedure; determine a data resource for the uplink data based on one ormore of the at least one PRACH resource, the preamble sequence, the typeof uplink data, or a size of the uplink data; and send, to a networkdevice using the at least one PRACH resource and the data resource, aRACH transmission that comprises the preamble sequence and the uplinkdata.